Sepsis-Induced T Cell Immunoparalysis: The Ins and Outs of Impaired T Cell Immunity

Identification and validation of autophagy-related genes in sepsis based on bioinformatics studies

We identified 14 key genes associated with mitochondrial autophagy in sepsis through differential analysis of the dataset and then analysed the identified genes for functional enrichment. The analysis of key genes and deeper analysis of key genes by molecular typing, Weighted Gene Correlation Network Analysis (WGCNA) and ceRNA were also carried out. We have also validated these key genes with clinical data. Finally, sepsis diagnostic models are constructed by combining key genes with machine learning methods. In addition, we discuss the importance of the immune system in sepsis and its relationship with signature genes, which opens up new directions for studying the role of the immune system in sepsis. Overall, our study adds new ideas to the diagnosis and treatment of sepsis.

Lower Plasma IL-32 Levels Linked to Better Survival in Sepsis

Background/Objectives: Interleukin-32 (IL-32) is a pro-inflammatory cytokine primarily produced by immune cells and involved in bacterial and viral infections. This study investigates whether plasma IL-32 is associated with sepsis severity and clinical outcomes. Methods: Plasma IL-32 levels were measured in 186 patients with systemic inflammatory response syndrome (SIRS), sepsis, or septic shock, as well as in 40 controls. The relationship between IL-32 levels and SARS-CoV-2 or bacterial infections, alongside underlying etiological conditions, was assessed. Results: Patients with liver cirrhosis exhibited elevated plasma IL-32 levels. After excluding these patients, IL-32 levels were lower in SIRS/sepsis patients compared to the controls. No significant differences in IL-32 levels were observed among SIRS, sepsis, and septic shock patients. Additionally, underlying conditions such as pancreatitis and cholangitis did not influence IL-32 levels. Patients with bloodstream bacterial infections, SARS-CoV-2 infections, or no documented infection had comparable IL-32 levels. Notably, higher IL-32 levels were associated with increased mortality. Conclusions: These findings suggest that a reduction in plasma IL-32 levels may be protective in SIRS/sepsis patients, as elevated levels are linked to poor survival outcomes.

Plasma proteomics in pediatric patients with sepsis- hopes and challenges

One of the main causes of morbidity and death in pediatric patients is sepsis. Of the 48.9 million cases of sepsis reported globally, 41.5% involve children under the age of five, with 2.9 million deaths associated with the disease. Clinicians must identify and treat patients at risk of sepsis or septic shock before late-stage organ dysfunction occurs since diagnosing sepsis in young patients is more difficult than in adult patients. As of right now, omics technologies that possess adequate diagnostic sensitivity and specificity can assist in locating biomarkers that indicate how the disease will progress clinically and how the patient will react to treatment. By identifying patients who are at a higher risk of dying or experiencing persistent organ dysfunction, risk stratification based on biomarkers generated from proteomics can enhance prognosis. A potentially helpful method for determining the proteins that serve as biomarkers for sepsis and formulating theories on the pathophysiological mechanisms behind complex sepsis symptoms is plasma proteomics.

A single-cell atlas of circulating immune cells over the first 2 months of age in extremely premature infants

Extremely premature infants (EPIs) who are born before 30 weeks of gestation are susceptible to infection; however, the trajectory of their peripheral immunity is poorly understood. Here, we undertook longitudinal analyses of immune cells from 250 μl of whole blood at 1 week, 1 month, and 2 months from 10 EPIs and compared these with samples from healthy adults and with preterm and full-term cord blood samples. Single-cell suspensions from individual samples were split to perform single-cell RNA sequencing, T and B cell receptor sequencing, and phosphoprotein mass cytometry. The trajectories of circulating T, B, myeloid, and natural killer cells in EPIs over the first 2 months of life were distinct from those of full-term infants. In EPIs, peripheral T cell development rapidly progressed over the first month of life, with an increase in the proportion of naïve CD4+, regulatory, and cycling T cells, accompanied by greater STAT5 (signal transducer and activator of transcription 5) signaling. EPI memory CD4+ T cells showed a T helper 1 (TH1) predominance compared with TH2 skewing of central memory-like T cells in full-term infants, and B cells from 2-month-old EPIs exhibited increased signatures of activation and differentiation. Both B and T cells from 2-month-old EPIs displayed increased interferon signatures compared with cells from full-term infants. In conclusion, we demonstrated the feasibility of longitudinal multiomic analyses in EPIs using minute amounts of blood and developed a resource describing peripheral immune development in EPIs that suggested ongoing activation in early life.

D 4 -CHIP REVEALS IMPAIRED T-CELL FUNCTION IN SEPSIS: INSIGHTS FROM PLASMA MICROENVIRONMENT ANALYSIS AND MITOCHONDRIAL-TARGETED THERAPY

ABSTRACT

Background: Sepsis, a systemic inflammation syndrome initiated by infection, poses significant challenges due to its intricate pathophysiology. T cells play a crucial role in combating infections during sepsis. Despite previous observations indicating T-cell dysfunction in sepsis, reliable in vitro detection methods were lacking, and the factors influencing these impairments remained unclear. Methods: We developed a novel method using the D 4 -Chip to assess sepsis T-cell migration function. This microfluidic platform enabled precise analysis of migration function under controlled conditions. Additionally, We explored the impact of the plasma microenvironment on T-cell behavior, along with the redox environment in sepsis, and assessed the potential efficacy of Mitoquinone mesylate (MitoQ), a mitochondrial-targeted drug. Results: Our findings revealed impaired migration function in sepsis T cells compared to healthy controls. Interestingly, sepsis plasma enhanced the migration of healthy T cells, yet incubation with healthy plasma did not fully restore migration impairments in sepsis T cells. Subsequent investigations uncovered a significant increase in NADH/NAD+ levels in sepsis T cells, with healthy T cells exposed to various sepsis plasma conditions also showing elevated NADH/NAD+ levels. Importantly, MitoQ normalized abnormal intracellular NADH/NAD+ levels and enhanced the migration ability of T cells. Conclusions: Short-term incubation with sepsis plasma does not directly inhibit T-cell migration but instead affects T-cell function by disrupting the intracellular redox environment. Improving the intracellular redox environment of sepsis patients contributes to restoring impaired migration and proliferation, with MitoQ demonstrating therapeutic potential.

Identification of Subtypes and Diagnostic Markers Related to Necroptosis in Sepsis

Sepsis is a serious systemic infection with a high mortality rate. More and more evidence suggested that necroptosis plays a crucial role in the pathogenesis and progression of sepsis. This study aimed to elucidate the biological function and clinical significance of necroptosis in sepsis, and identify new potential biomarkers to improve the diagnosis and treatment of sepsis. Firstly, we identified 40 differentially expressed necroptosis related genes (DENRGs). Subsequently, a protein interaction (PPI) network of 40 DENRGs was constructed. Based on the key NRGs in the PPI network, the LASSO algorithm was used to screen eight diagnostic-related NRGs in sepsis, and a diagnostic model and risk score were constructed. The ROC analysis results indicated that the eight NRGs diagnostic model has good diagnostic performance (AUC = 0.955). There is a significant difference in risks core between normal samples and sepsis patients. The results of immune infiltration analysis showed that eight diagnostic-related NRGs were significantly correlated with multiple immune cells. Given the clinical significance of necroptosis in sepsis, we identified two molecular subtypes of sepsis based on eight NRGs. The necroptosis score of subtype 1 is significantly lower than that of subtype 2, while the immune score of subtype 1 is significantly higher than that of subtype 2. In summary, we developed and validated a diagnostic model and risk score based on eight NRGs, and identified two completely different subtypes associated with sepsis. Our research may provide new insights into the mechanisms of necroptosis in sepsis and the identification of potential biomarkers.

Malocclusion Worsens Survival Following Sepsis Due to the Disruption of Innate and Acquired Immunity

Sepsis is a severe condition with high mortality, in which immune dysfunction plays a critical role. Poor oral health has been linked to frailty, but its impact on sepsis outcomes remains unclear. Therefore, we used a mouse model of malocclusion and sepsis to investigate how tooth loss affects immune responses during sepsis. Adult male C57BL/6 mice were divided into four groups: Control, Malocclusion (Mal), Sepsis (CS), and Malocclusion with Sepsis (Mal + CS). Malocclusion was induced by tooth extraction, and sepsis was induced using cecal slurry injection. We assessed survival rates, immune cell counts, and biochemical markers. The Mal + CS group exhibited significantly lower survival rates and greater weight loss compared to the CS group. The flow cytometry showed reduced neutrophils, monocytes, and T cells in the Mal + CS group. Elevated ALT and AST levels indicated liver damage. No significant differences in bacterial loads were observed, but immune suppression was exacerbated in the Mal + CS group. Malocclusion worsens sepsis outcomes by impairing both innate and adaptive immune responses. These findings emphasize the importance of oral health in improving sepsis prognosis and immune function during critical illnesses.

Moxifloxacin plus Cordyceps polysaccharide ameliorate intestinal barrier damage due to abdominal infection via anti-inflammation and immune regulation under simulated microgravity

BACKGROUND

Currently, there is limited research on the impact of abdominal infection on intestinal damage under microgravity conditions. Cordyceps polysaccharide (CPS), the main active ingredient of Cordyceps, has demonstrated various pharmacological effects, including anti-inflammatory, antioxidant, and immunomodulatory properties. Moxifloxacin (MXF) is a fourth-generation quinolone antibiotic that is believed to have a dual regulatory effect on immune system activation and suppression. Our objective was to investigate the effects of MXF plus CPS on the intestinal barrier damage due to abdominal infection under microgravity.

METHODS

The hindlimb unloading model in rats was employed to simulate microgravity. The rat model of abdominal infection was established by cecal ligation and puncture (CLP). MXF, CPS and the combination of the two drugs were used to treat CLP-rats in simulated microgravity. We assessed histopathological changes of ileum by hematoxylin and eosin staining. The intestinal ultrastructure was observed under transmission electron microscopy. Additionally, the expression of intestinal barrier proteins RegIII α/γ and MUC2 was detected by Western blot analysis, while the localization of these proteins within the ileum was examined using immunohistochemistry. Cytometric bead array (CBA) was employed to detect cytokine including IL-6, TNF-α, IL-1β, IL-1α, CXCL-1, MCP-1, IL-17A, IL-18, and IL-33. Flow cytometry analysis was conducted to determine the percentages of Treg cells, M1 macrophages, M2 macrophages, T cells and CD8+T cells.

RESULTS

The results showed that compared with the normal gravity groups, the simulated microgravity groups exhibited a significant decrease in RegIII α/γ protein expression, an increase in M1 macrophage frequency, and elevated levels of TNF-α, IL-1α, MCP-1 and IL-6. Notably, the combined application of MXF and CPS effectively mitigated intestinal barrier damage in CLP-rats exposed to microgravity, as evidenced by alleviated ultrastructural and pathological impairments in ileum, along with increased expression of key intestinal barrier proteins MUC2 and RegIII α/γ. Furthermore, the combination therapy enhances the proportion of T cells, CD8+T cells, and M2 macrophages in septic rats exposed to simulated microgravity while reducing the frequency of Treg cells and M1 macrophages. MXF plus CPS also led to a reduction of proinflammatory cytokines and chemokines, including IL-6, TNF-α, IL-1β, IL-1α, CXCL-1, MCP-1, IL18, and IL33.

CONCLUSION

Our study showed that MXF plus CPS exhibited a protective effect on intestinal barrier damage due to abdominal infection under microgravity, potentially attributed to its anti-inflammatory properties and immune regulatory mechanisms. These findings may provide insights into the development of drugs targeting abdominal infections in the space environment.

Arginine metabolism in myeloid cells in health and disease

Metabolic flexibility is key for the function of myeloid cells. Arginine metabolism is integral to the regulation of myeloid cell responses. Nitric oxide (NO) production from arginine is vital for the antimicrobial and pro-inflammatory responses. Conversely, the arginase 1 (ARG1)-dependent switch between the branch of NO production and polyamine synthesis downregulates inflammation and promotes recovery of tissue homeostasis. Creatine metabolism is key for energy supply and proline metabolism is required for collagen synthesis. Myeloid ARG1 also regulates extracellular arginine availability and T cell responses in parasitic diseases and cancer. Cancer, surgery, sepsis and persistent inflammation in chronic inflammatory diseases, such as neuroinflammatory diseases or arthritis, are associated with dysregulation of arginine metabolism in myeloid cells. Here, we review current knowledge on arginine metabolism in different myeloid cell types, such as macrophages, neutrophils, microglia, osteoclasts, tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs) and myeloid-derived suppressor cells (MDSCs). A deeper understanding of the function of arginine metabolism in myeloid cells will improve our knowledge on the pathology of several diseases and may set the platform for novel therapeutic applications.

Identification of lethality-related m7G methylation modification patterns and the regulatory features of immune microenvironment in sepsis

Objectives

N7-methylguanosine (m7G) modification is closely related to the occurrence of human diseases, but its roles in sepsis remain unclear. This study aimed to explore the patterns of lethality-related m7G regulatory factor-mediated RNA methylation modification and immune microenvironment regulatory features in sepsis.

Methods

Three sepsis-related datasets (E-MTAB-4421 and E-MTAB-4451 as training sets and GSE185263 as a validation set) were collected, and differentially expressed m7G-related genes were analyzed between survivors and non-survivors. Lethality-related m7G signature genes were then screened using machine learning methods, followed by the construction of a survival recognition model. Additionally, differences in immune cell distribution were determined and differentially expressed genes (DEGs) between different subtypes were analyzed. Weighted gene co-expression network analysis (WGCNA) was used to select important modules and related hub genes.

Results

In total, 10 differentially expressed m7G-related genes were identified between the survivors and non-survivors, and after further analysis, EIF4G3, EIF4E3, NSUN2, NUDT4, and GEMIN5 were identified as the optimal lethality-related m7G genes. A survival status diagnostic model was then constructed with a combined AUC of 0.678. Fifteen types of immune cells were significantly different between survivors and non-survivors. Sepsis samples were classified into two subtypes, with 22 types of immune cells showing significant differences. Subsequently, 1707 DEGs were identified between the two subtypes, which were significantly enriched in 91 GO terms and 16 KEGG pathways. Finally, the green module with |correlation| > 0.3 was found to be closely related to the subtypes and survival status; further, the top10 hub genes were obtained.

Conclusion

The constructed survival status diagnostic model based on the five lethality-related m7G signature genes may help predict the survival status of patients, and the 10 hub genes obtained may be potential therapeutic targets for sepsis.

Combining ulinastatin with TIENAM improves the outcome of sepsis induced by cecal ligation and puncture in mice by reducing inflammation and regulating immune responses

Despite the high mortality associated with sepsis, effective and targeted treatments remain scarce. The use of conventional antibiotics such as TIENAM (imipenem and cilastatin sodium for injection, TIE) is challenging because of the increasing bacterial resistance, which diminishes their efficacy and leads to adverse effects. Our previous studies demonstrated that ulinastatin (UTI) exerts a therapeutic impact on sepsis by reducing systemic inflammation and modulating immune responses. In this study, we examined the possibility of administering UTI and TIE after inducing sepsis in a mouse model using cecal ligation and puncture (CLP). We assessed the rates of survival, levels of inflammatory cytokines, the extent of tissue damage, populations of immune cells, microbiota in ascites, and important signaling pathways. The combination of UTI and TIE significantly improved survival rates and reduced inflammation and bacterial load in septic mice, indicating potent antimicrobial properties. Notably, the survival rates of UTI+TIE-treated mice increased from 10 % to 75 % within 168 h compared to those of mice that were subjected to CLP. The dual treatment successfully regulated the levels of inflammatory indicators (interleukin [IL]-6, IL-1β, and tumor necrosis factor [TNF]-α) and immune cell numbers by reducing B cells, natural killer cells, and TNFR2+ Treg cells and increasing CD8+ T cells. Additionally, the combination of UTI and TIE alleviated tissue damage, reduced bacterial load in the peritoneal cavity, and suppressed the NF-κB signaling pathway. Our findings indicate that UTI and TIE combination therapy can significantly enhance sepsis outcomes by reducing inflammation and boosting the immune system. The results offer a promising therapeutic approach for future sepsis treatment.

Causal relationship between lymphocyte subsets and the risk of sepsis: A Mendelian randomization study

Recent empirical research posits a link between lymphocyte subgroups and both the incidence and prognosis of sepsis. Nevertheless, the potential influence of multiple confounding variables obscures any clear causative correlation. Utilizing a 2-sample Mendelian randomization approach, we conducted a meta-analysis of lymphocyte subgroups. In a genome-wide association study, flow cytometry was applied to a lymphocyte subgroup comprising 3757 Sardinians to identify genes influenced by blood immune cells. The sepsis meta-analysis data were sourced from the UK Biobank database, including 11,643 treatment groups and 47,841 control groups. Inverse variance-weighted, Mendelian randomization-Egger regression, weighted median, simple mode, and weighted mode methods were deployed to ascertain the causative relationship between lymphocyte subgroup and sepsis. Cochran Q test, the Mendelian randomization-Egger intercept test, and funnel plots were leveraged to assess the robustness of study findings. The inverse variance-weighted analysis disclosed that the absolute count of CD4 regulatory T cells (CD4 Treg AC) within the lymphocyte subgroup has a causative link to an elevated risk of sepsis, with an odds ratio of 1.08 and a 95% confidence interval of 1.02 to 1.15 (P = .011). Compared to individuals not subjected to this factor, those exposed to CD4 Treg AC have a marginally elevated sepsis risk by approximately 0.08%. No causative relationships were observed between sepsis risk and the absolute counts of other lymphocyte subgroups such as CD8+ T cells, CD4+ CD8dim T cells, natural killer T cells, B cells (B cell absolute count), and HLA DR+ natural killer cells. The 2-sample Mendelian randomization study indicated a causal relationship between the level of CD4 Treg AC and the increased risk of sepsis. The elevation in circulating lymphocyte subgroups suggests higher susceptibility to sepsis, affirming the immune susceptibility inherent to this condition. The findings from our study may propose potential targets for diagnosis and intervention of sepsis.

The neutrophil-to-lymphocyte ratio levels over time correlate to all-cause hospital mortality in sepsis

Objective

This research aims to investigate the prognosis value using the time-weighted average neutrophil-to-lymphocyte ratio (TWA-NLR) for predicting all-cause hospital mortality among sepsis patients. Data were analyzed through the use of the eICU Collaborative Research Database (eICU-CRD 2.0) as well as Medical Information Mart for Intensive Care IV 2.2 (MIMIC-IV 2.2).

Methods

Septic patients from both eICU-CRD 2.0 as well as MIMIC-IV 2.2 databases were included. The neutrophil-to-lymphocyte ratios (NLR) were available for analysis, utilizing complete blood counts obtained on days one, four, and seven following ICU admission. The TWA-NLR was computed at the end of the seven days, and patients were then stratified based on TWA-NLR thresholds. 90-day all-cause mortality during hospitalization was the primary objective, with 60-day all-cause hospital mortality as a secondary objective. The correlation between TWA-NLR and sepsis patients' primary outcome was analyzed using univariable and multivariable Cox proportional hazard regressions. A restricted cubic spline (RCS) analysis was conducted in an attempt to confirm this association further, and subgroup analyses were employed to evaluate the correlation across various comorbidity groups.

Results

3921 patients were included from the eICU-CRD 2.0, and the hospital mortality rate was 20.8 %. Both multivariable as well as univariable Cox proportional hazard regression analyses revealed that TWA-NLR was independently correlated with 90-day all-cause hospital mortality, yielding a hazard ratio (HR) of 1.02 (95 % CI 1.01-1.02, P-value<0.01) as well as 1.12 (95 % CI 1.01-1.15, P-value<0.01), respectively. The RCS analysis demonstrated a significant nonlinear relationship between TWA-NLR and 90-day all-cause hospital mortality risk. The study subjects were divided into higher (>10.5) and lower (≤10.5) TWA-NLR cohorts. A significantly decreased incidence of 90-day all-cause hospital mortality (HR = 0.56, 95 % CI 0.48-0.64, P-value<0.01) and longer median survival time (40 days vs 24 days, P-value<0.05) were observed in the lower TWA-NLR cohort. However, septic patients with chronic pulmonary (interaction of P-value = 0.009) or renal disease (interaction of P-value = 0.008) exhibited significant interactive associations between TWA-NLR and 90-day all-cause hospital mortality, suggesting the predictive power of TWA-NLR may be limited in these subgroups. The MIMIC-IV 2.2 was utilized as a validation cohort and exhibited a similar pattern.

Conclusion

Our findings suggest that TWA-NLR is a powerful and independent prognostic indicator for 90-day all-cause hospital mortality among septic patients, and the TWA-NLR cutoff value may prove a useful method for identifying high-risk septic patients.

U-shaped correlation of lymphocyte count with all-cause hospital mortality in sepsis and septic shock patients: a MIMIC-IV and eICU-CRD database study

BACKGROUND

In sepsis, the relationship between lymphocyte counts and patient outcomes is complex. Lymphocytopenia and lymphocytosis significantly influence survival, illustrating the dual functionality of lymphocytes in responding to infections. This study investigates this complex interaction, focusing on how variations in lymphocyte counts correlate with all-cause hospital mortality among sepsis patients.

METHODS

This retrospective cohort study analyzed data from two extensive critical care databases: the Medical Information Mart for Intensive Care IV 2.0 (MIMIC-IV 2.0) from Beth Israel Deaconess Medical Center, Boston, Massachusetts, and the eICU Collaborative Research Database (eICU-CRD), which was Multi-center database from over 200 hospitals across the United States conducted by Philips eICU Research Institute. We included adult patients aged 18 years and older who met the Sepsis-3 criteria, characterized by documented or suspected infection and a Sequential Organ Failure Assessment (SOFA) score of 2 or higher. Sepsis patients were categorized into quartiles based on lymphocyte counts. The primary outcome was all-cause mortality in the hospital, with 90 and 60-day all-cause mortality as the secondary outcomes. Univariable and multivariable Cox proportional hazard regressions were utilized to assess lymphocyte counts' impact on hospital mortality. An adjusted restricted cubic spline (RCS) analysis was performed to elucidate this relationship further. Subgroup analyses were also conducted to explore the association across various comorbidity groups among sepsis and septic shock patients.

RESULTS

Our study included 37,054 patients, with an observed in-hospital mortality rate of 16.6%. Univariable and multivariable Cox proportional hazard regression models showed that lymphocyte counts were independently associated with in-hospital mortality (HR = 1.04, P < 0.01; HR = 1.06, P < 0.01). RCS regression analysis revealed a U-shaped relationship between lymphocyte levels and hospital mortality risk in sepsis and septic shock patients (P for overall < 0.001, P for nonliner < 0.01; P for overall = 0.002, P for nonliner = 0.014). Subgroup analyses revealed that elevated lymphocyte counts correlated with increased hospital mortality among sepsis patients with liver disease and requiring renal replacement therapy (P for overall = 0.021, P for nonliner = 0.158; P for overall = 0.025, P for nonliner = 0.759). These findings suggest that lymphocytes may have enhanced prognostic value in specific subsets of critically ill sepsis patients.

CONCLUSION

Our findings demonstrate that lymphocyte counts are a significant independent predictor of hospital mortality in sepsis and septic shock patients. We observed a U-shaped association between lymphocyte levels and mortality risk, indicating that high and low counts are linked to increased mortality. This result highlights the complex role of lymphocytes in sepsis outcomes and suggests the need for further investigation into the underlying mechanisms and potential therapeutic approaches. Integrating lymphocyte count assessment into risk stratification algorithms and clinical decision support tools could enhance the early identification of high-risk sepsis patients.

TEMPORAL CHANGES IN INNATE AND ADAPTIVE IMMUNITY DURING SEPSIS AS DETERMINED BY ELISPOT

ABSTRACT

Background: The inability to evaluate host immunity in a rapid quantitative manner in patients with sepsis has severely hampered development of novel immune therapies. The enzyme-linked immunospot (ELISpot) assay is a functional bioassay that measures the number of cytokine-secreting cells and the relative amount of cytokine produced at the single-cell level. A key advantage of ELISpot is its excellent dynamic range enabling a more precise quantifiable assessment of host immunity. Herein, we tested the hypothesis that the ELISpot assay can detect dynamic changes in both innate and adaptive immunity as they often occur during sepsis. We also tested whether ELISpot could detect the effect of immune drug therapies to modulate innate and adaptive immunity. Methods: Mice were made septic using sublethal cecal ligation and puncture. Blood and spleens were harvested serially, and ex vivo interferon γ and TNF-α production were compared by ELISpot and enzyme-linked immunosorbent assay. The capability of ELISpot to detect changes in innate and adaptive immunity due to in vivo immune therapy with dexamethasone, IL-7, and arginine was also evaluated. Results: ELISpot confirmed a decreased innate and adaptive immunity responsiveness during sepsis progression. More importantly, ELISpot was also able to detect changes in adaptive and innate immunity in response to immune-modulatory reagents, for example, dexamethasone, arginine, and IL-7, in a readily quantifiable manner, as predicted by the reagents known mechanisms of action. ELISpot and enzyme-linked immunosorbent assay results tended to parallel one another although some differences were noted. Conclusion: ELISpot offers a unique capability to assess the functional status of both adaptive and innate immunity over time. The results presented herein demonstrate that ELISpot can also be used to detect and follow the in vivo effects of drugs to ameliorate sepsis-induced immune dysfunction. This capability would be a major advance in guiding new immune therapies in sepsis.

The potential immunological mechanisms of sepsis

Sepsis is described as a life-threatening organ dysfunction and a heterogeneous syndrome that is a leading cause of morbidity and mortality in intensive care settings. Severe sepsis could incite an uncontrollable surge of inflammatory cytokines, and the host immune system's immunosuppression could respond to counter excessive inflammatory responses, characterized by the accumulated anti-inflammatory cytokines, impaired function of immune cells, over-proliferation of myeloid-derived suppressor cells and regulatory T cells, depletion of immune effector cells by different means of death, etc. In this review, we delve into the underlying pathological mechanisms of sepsis, emphasizing both the hyperinflammatory phase and the associated immunosuppression. We offer an in-depth exploration of the critical mechanisms underlying sepsis, spanning from individual immune cells to a holistic organ perspective, and further down to the epigenetic and metabolic reprogramming. Furthermore, we outline the strengths of artificial intelligence in analyzing extensive datasets pertaining to septic patients, showcasing how classifiers trained on various clinical data sources can identify distinct sepsis phenotypes and thus to guide personalized therapy strategies for the management of sepsis. Additionally, we provide a comprehensive summary of recent, reliable biomarkers for hyperinflammatory and immunosuppressive states, facilitating more precise and expedited diagnosis of sepsis.

A comprehensive analysis of the immune system in healthy Vietnamese people

Lifestyle, diet, socioeconomic status and genetics all contribute to heterogeneity in immune responses. Vietnam is plagued with a variety of health problems, but there are no available data on immune system values in the Vietnamese population. This study aimed to establish reference intervals for immune cell parameters specific to the healthy Vietnamese population by utilizing multi-color flow cytometry (MCFC). We provide a comprehensive analysis of total leukocyte count, quantitative and qualitative shifts within lymphocyte subsets, serum and cytokine and chemokine levels and functional attributes of key immune cells including B cells, T cells, natural killer (NK) cells and their respective subpopulations. By establishing these reference values for the Vietnamese population, these data contribute significantly to our understanding of the human immune system variations across diverse populations. These data will be of substantial comparative value and be instrumental in developing personalized medical approaches and optimizing diagnostic strategies for individuals based on their unique immune profiles.

Causal associations between severe mental illness and sepsis: a Mendelian randomization study

Objective

SMI (severe mental illness) has been identified as a risk factor for sepsis in observational studies; however, the causal association between them has yet to be firmly established. We conducted MR (mendelian randomization) to unveil the causal relationship between SMI and sepsis as well as sepsis mortality.

Methods

GWAS (Genome-wide association) data for major depression and schizophrenia were selected as exposure. GWAS data for sepsis and sepsis mortality were selected as outcome. Genetic variants significantly associated with the exposure (P value<1x10-6) were selected as instruments. We primarily employed the IVW (inverse-variance weighted) method for analysis. Furthermore, we employed Cochrane's Q test to assess heterogeneity and the MR-Egger intercept test to identify horizontal pleiotropy.

Results

We selected 108 SNPs (single nucleotide polymorphism) used to predict major depression and 260 SNPs that predicted schizophrenia. Genetically predicted major depression was suggestively linked to a higher sepsis risk (OR=1.13, 95%CI 1.02-1.26, P=0.023). In contrast, MR analysis did not find an association between schizophrenia and sepsis risk (OR=1.00, 95%CI 0.97-1.04, P=0.811). Furthermore, no significant causal evidence was found for genetically predicted SMI in sepsis mortality. Moreover, no heterogeneity and horizontal pleiotropy were detected.

Conclusion

Our research revealed a suggestive association between genetically predicted major depression and an elevated risk of sepsis in individuals of European ancestry. This finding can serve as a reminder for clinicians to consider the possibility of subsequent infection and sepsis in depressive patients, which may help reduce the incidence of sepsis in individuals with depression.

Moderate Exercise Modulates Inflammatory Responses and Improves Survival in a Murine Model of Acute Pneumonia

OBJECTIVES

An association between physical inactivity and worse outcome during infectious disease has been reported. The effect of moderate exercise preconditioning on the immune response during an acute pneumonia in a murine model was evaluated.

SETTING

Laboratory experiments.

SUBJECTS

C57BL6/j male mice.

INTERVENTIONS

Six-week-old C57BL/6J mice were divided in two groups: an exercise group and a control group. In the exercise group, a moderate, progressive, and standardized physical exercise was applied for 8 weeks. It consisted in a daily treadmill training lasting 60 minutes and with an intensity of 65% of the maximal theoretical oxygen uptake. Usual housing recommendation were applied in the control group during the same period. After 8 weeks, pneumonia was induced in both groups by intratracheal instillation of a fixed concentration of a Klebsiella pneumoniae (5 × 103 colony-forming unit) solution.

MEASUREMENTS AND MAIN RESULTS

Mice preconditioned by physical exercise had a less sever onset of pneumonia as shown by a significant decrease of the Mouse Clinical Assessment Severity Score and had a significantly lower mortality compared with the control group (27% vs. 83%; p = 0.019). In the exercise group, we observed a significantly earlier but transient recruitment of inflammatory immune cells with a significant increase of neutrophils, CD4+ cells and interstitial macrophages counts compared with control group. Lung tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-10 were significantly decreased at 48 hours after pneumonia induction in the exercise group compared with the control group.

CONCLUSIONS

In our model, preconditioning by moderate physical exercise improves outcome by reducing the severity of acute pneumonia with an increased but transient activation of the innate immune response.

Scd-1 deficiency promotes the differentiation of CD8+ T effector

The impact of various fatty acid types on adaptive immunity remains uncertain, and their roles remain unelucidated. Stearoyl-CoA desaturase (Scd) is a Δ-9 desaturase, which is a key rate-limiting enzyme for the conversion of saturated fatty acids (SFA) to monounsaturated fatty acids (MUFA) in the fatty acid de novo synthesis. Scd-1 converts stearic acid (SA) and palmitic acid (PA) to oleic acid (OA) and palmitoleic acid (PO), respectively. In this study, through a series of experiments, we showed that Scd-1 and its resulting compound, OA, have a substantial impact on the transformation of CD8+ naïve T cells into effector T cells. Inactivation of Scd-1 triggers the specialization of CD8+ T cells into the Teff subset, enhancing the effector function and mitochondrial metabolism of Teff cells, and OA can partially counteract this. A deeper understanding of lipid metabolism in immune cells and its impact on cell function can lead to new therapeutic approaches for controlling the immune response and improving prognosis.

A pairwise cytokine code explains the organism-wide response to sepsis

Sepsis is a systemic response to infection with life-threatening consequences. Our understanding of the molecular and cellular impact of sepsis across organs remains rudimentary. Here, we characterize the pathogenesis of sepsis by measuring dynamic changes in gene expression across organs. To pinpoint molecules controlling organ states in sepsis, we compare the effects of sepsis on organ gene expression to those of 6 singles and 15 pairs of recombinant cytokines. Strikingly, we find that the pairwise effects of tumor necrosis factor plus interleukin (IL)-18, interferon-gamma or IL-1β suffice to mirror the impact of sepsis across tissues. Mechanistically, we map the cellular effects of sepsis and cytokines by computing changes in the abundance of 195 cell types across 9 organs, which we validate by whole-mouse spatial profiling. Our work decodes the cytokine cacophony in sepsis into a pairwise cytokine message capturing the gene, cell and tissue responses of the host to the disease.

Lung single-cell RNA profiling reveals response of pulmonary capillary to sepsis-induced acute lung injury

Background

Sepsis-induced acute lung injury (ALI) poses a significant threat to human health. Endothelial cells, especially pulmonary capillaries, are the primary barriers against sepsis in the lungs. Therefore, investigating endothelial cell function is essential to understand the pathophysiological processes of sepsis-induced ALI.

Methods

We downloaded single-cell RNA-seq expression data from GEO with accession number GSE207651. The mice underwent cecal ligation and puncture (CLP) surgery, and lung tissue samples were collected at 0, 24, and 48 h. The cells were annotated using the CellMarker database and FindAllMarkers functions. GO enrichment analyses were performed using the Metascape software. Gene set enrichment Analysis (GSEA) and variation Analysis (GSVA) were performed to identify differential signaling pathways. Differential expression genes were collected with the "FindMarkers" function. The R package AUCell was used to score individual cells for pathway activities. The Cellchat package was used to explore intracellular communication.

Results

Granulocytes increased significantly as the duration of endotoxemia increased. However, the number of T cells, NK cells, and B cells declined. Pulmonary capillary cells were grouped into three sub-clusters. Capillary-3 cells were enriched in the sham group, but declined sharply in the CLP.24 group. Capillary-1 cells peaked in the CLP.24 group, while Capillary-2 cells were enriched in the CLP.48 group. Furthermore, we found that Cd74+ Capillary-3 cells mainly participated in immune interactions. Plat+ Capillary-1 and Clec1a+ Capillary-2 are involved in various physiological processes. Regarding cell-cell interactions, Plat+ Capillary-1 plays the most critical role in granulocyte adherence to capillaries during ALI. Cd74+ Capillary cells expressing high levels of major histocompatibility complex (MHC) and mainly interacted with Cd8a+ T cells in the sham group.

Conclusion

Plat+ capillaries are involved in the innate immune response through their interaction with neutrophils via ICAM-1 adhesion during endotoxemia, while Cd74+ capillaries epxressed high level of MHC proteins play a role in adaptive immune response through their interaction with T cells. However, it remains unclear whether the function of Cd74+ capillaries leans towards immunity or tolerance, and further studies are needed to confirm this.

Elucidating common pathogenic transcriptional networks in infective endocarditis and sepsis: integrated insights from biomarker discovery and single-cell RNA sequencing

Background

Infective Endocarditis (IE) and Sepsis are two closely related infectious diseases, yet their shared pathogenic mechanisms at the transcriptional level remain unclear. This research gap poses a barrier to the development of refined therapeutic strategies and drug innovation.

Methods

This study employed a collaborative approach using both microarray data and single-cell RNA sequencing (scRNA-seq) data to identify biomarkers for IE and Sepsis. It also offered an in-depth analysis of the roles and regulatory patterns of immune cells in these diseases.

Results

We successfully identified four key biomarkers correlated with IE and Sepsis, namely CD177, IRAK3, RNASE2, and S100A12. Further investigation revealed the central role of Th1 cells, B cells, T cells, and IL-10, among other immune cells and cytokines, in the pathogenesis of these conditions. Notably, the small molecule drug Matrine exhibited potential therapeutic effects by targeting IL-10. Additionally, we discovered two Sepsis subgroups with distinct inflammatory responses and therapeutic strategies, where CD177 demonstrated significant classification value. The reliability of CD177 as a biomarker was further validated through qRT-PCR experiments.

Conclusion

This research not only paves the way for early diagnosis and treatment of IE and Sepsis but also underscores the importance of identifying shared pathogenic mechanisms and novel therapeutic targets at the transcriptional level. Despite limitations in data volume and experimental validation, these preliminary findings add new perspectives to our understanding of these complex diseases.

Cytokine Storm and Sepsis-Induced Multiple Organ Dysfunction Syndrome

There is extensive overlap of clinical features among familial or primary HLH (pHLH), reactive or secondary hemophagocytic lymphohistiocytosis (sHLH) [including macrophage activation syndrome (MAS) related to rheumatic diseases], and hyperferritinemic sepsis-induced multiple organ dysfunction syndrome (MODS); however, the distinctive pathobiology that causes hyperinflammatory process in each condition requires careful considerations for therapeutic decision-making. pHLH is defined by five or more of eight HLH-2004 criteria [1], where genetic impairment of natural killer (NK) cells or CD8+ cytolytic T cells results in interferon gamma (IFN-γ)-induced hyperinflammation regardless of triggering factors. Cytolytic treatments (e.g., etoposide) or anti-IFN-γ monoclonal antibody (emapalumab) has been effectively used to bridge the affected patients to hematopoietic stem cell transplant. Secondary forms of HLH also have normal NK cell number with decreased cytolytic function of varying degrees depending on the underlying and triggering factors. Although etoposide was uniformly used in sHLH/MAS in the past, the treatment strategy in different types of sHLH/MAS is increasingly streamlined to reflect the triggering/predisposing conditions, severity/progression, and comorbidities. Accordingly, in hyperferritinemic sepsis, the combination of hepatobiliary dysfunction (HBD) and disseminated intravascular coagulation (DIC) reflects reticuloendothelial system dysfunction and defines sepsis-associated MAS. It is demonstrated that as the innate immune response to infectious organism prolongs, it results in reduction in T cells and NK cells with subsequent lymphopenia even though normal cytolytic activity continues (Figs. 30.1, 30.2, 30.3, and 30.4). These changes allow free hemoglobin and pathogens to stimulate inflammasome activation in the absence of interferon-γ (IFN-γ) production that often responds to source control, intravenous immunoglobulin (IVIg), plasma exchange, and interleukin 1 receptor antagonist (IL-1Ra), similar to non-EBV, infection-induced HLH.

Temporal Changes in Innate and Adaptive Immunity During Sepsis as Determined by ELISpot

Background

The inability to evaluate host immunity in a rapid quantitative manner in patients with sepsis has severely hampered development of novel immune therapies. The ELISpot assay is a functional bioassay that measures the number of cytokine-secreting cells and the relative amount of cytokine produced at the single-cell level. A key advantage of ELISpot is its excellent dynamic range enabling a more precise quantifiable assessment of host immunity. Herein, we tested the hypothesis on whether the ELISpot assay can detect dynamic changes in both innate and adaptive immunity as they often occur during sepsis. We also tested whether ELISpot could detect the effect of immune drug therapies to modulate innate and adaptive immunity.

Methods

Mice were made septic using sublethal cecal ligation and puncture (CLP). Blood and spleens were harvested serially and ex vivo IFN-γ and TNF-α production were compared by ELISpot and ELISA. The capability of ELISpot to detect changes in innate and adaptive immunity due to in vivo immune therapy with dexamethasone, IL-7, and arginine was also evaluated.

Results

ELISpot confirmed a decreased innate and adaptive immunity responsiveness during sepsis progression. More importantly, ELISpot was also able to detect changes in adaptive and innate immunity in response to immune-modulatory reagents, for example dexamethasone, arginine, and IL-7 in a readily quantifiable manner, as predicted by the reagents known mechanisms of action. ELISpot and ELISA results tended to parallel one another although some differences were noted.

Conclusion

ELISpot offers a unique capability to assess the functional status of both adaptive and innate immunity over time. The results presented herein demonstrate that ELISpot can also be used to detect and follow the in vivo effects of drugs to ameliorate sepsis-induced immune dysfunction. This capability would be a major advance in guiding new immune therapies in sepsis.

Novel tripeptide RKH derived from Akkermansia muciniphila protects against lethal sepsis

OBJECTIVE

The pathogenesis of sepsis is complex, and the sepsis-induced systemic proinflammatory phase is one of the key drivers of organ failure and consequent mortality. Akkermansia muciniphila (AKK) is recognised as a functional probiotic strain that exerts beneficial effects on the progression of many diseases; however, whether AKK participates in sepsis pathogenesis is still unclear. Here, we evaluated the potential contribution of AKK to lethal sepsis development.

DESIGN

Relative abundance of gut microbial AKK in septic patients was evaluated. Cecal ligation and puncture (CLP) surgery and lipopolysaccharide (LPS) injection were employed to establish sepsis in mice. Non-targeted and targeted metabolomics analysis were used for metabolites analysis.

RESULTS

We first found that the relative abundance of gut microbial AKK in septic patients was significantly reduced compared with that in non-septic controls. Live AKK supplementation, as well as supplementation with its culture supernatant, remarkably reduced sepsis-induced mortality in sepsis models. Metabolomics analysis and germ-free mouse validation experiments revealed that live AKK was able to generate a novel tripeptide Arg-Lys-His (RKH). RKH exerted protective effects against sepsis-induced death and organ damage. Furthermore, RKH markedly reduced sepsis-induced inflammatory cell activation and proinflammatory factor overproduction. A mechanistic study revealed that RKH could directly bind to Toll-like receptor 4 (TLR4) and block TLR4 signal transduction in immune cells. Finally, we validated the preventive effects of RKH against sepsis-induced systemic inflammation and organ damage in a piglet model.

CONCLUSION

We revealed that a novel tripeptide, RKH, derived from live AKK, may act as a novel endogenous antagonist for TLR4. RKH may serve as a novel potential therapeutic approach to combat lethal sepsis after successfully translating its efficacy into clinical practice.

Nicotinamide mononucleotide as a therapeutic agent to alleviate multi-organ failure in sepsis

BACKGROUND

Sepsis-caused multi-organ failure remains the major cause of morbidity and mortality in intensive care units with limited therapeutics. Nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD+), has been recently reported to be protective in sepsis; however, its therapeutic effects remain to be determined. This study sought to investigate the therapeutic effects of NMN in septic organ failure and its underlying mechanisms.

METHODS

Sepsis was induced by feces-injection-in-peritoneum in mice. NMN was given after an hour of sepsis onset. Cultured neutrophils, macrophages and endothelial cells were incubated with various agents.

RESULTS

We demonstrate that administration of NMN elevated NAD+ levels and reduced serum lactate levels, oxidative stress, inflammation, and caspase-3 activity in multiple organs of septic mice, which correlated with the attenuation of heart dysfunction, pulmonary microvascular permeability, liver injury, and kidney dysfunction, leading to lower mortality. The therapeutic effects of NMN were associated with lower bacterial burden in blood, and less ROS production in septic mice. NMN improved bacterial phagocytosis and bactericidal activity of macrophages and neutrophils while reducing the lipopolysaccharides-induced inflammatory response of macrophages. In cultured endothelial cells, NMN mitigated mitochondrial dysfunction, inflammation, apoptosis, and barrier dysfunction induced by septic conditions, all of which were offset by SIRT3 inhibition.

CONCLUSION

NAD+ repletion with NMN prevents mitochondrial dysfunction and restrains bacterial dissemination while limiting inflammatory damage through SIRT3 signaling in sepsis. Thus, NMN may represent a therapeutic option for sepsis.

Comprehensive analysis of immune cell landscapes revealed that immune cell ratio eosinophil/B.cell.memory is predictive of survival in sepsis

BACKGROUND

Immune dysregulation is a feature of sepsis. However, a comprehensive analysis of the immune landscapes in septic patients has not been conducted.

OBJECTIVES

This study aims to explore the abundance ratios of immune cells in sepsis and investigate their clinical value.

METHODS

Sepsis transcriptome data sets were downloaded from the NCBI GEO database. The immunedeconv R package was employed to analyze the abundance of immune cells in sepsis patients and calculate the ratios of different immune cell types. Differential analysis of immune cell ratios was performed using the t test. The Spearman rank correlation coefficient was utilized to find the relationships between immune cell abundance and pathways. The prognostic significance of immune cell ratios for patient survival probability was assessed using the log-rank test. In addition, differential gene expression was performed using the limma package, and gene co-expression analysis was executed using the WGCNA package.

RESULTS

We found significant changes in immune cell ratios between sepsis patients and healthy controls. Some of these ratios were associated with 28-day survival. Certain pathways showed significant correlations with immune cell ratios. Notably, six immune cell ratios demonstrated discriminative ability for patients with systemic inflammatory response syndrome (SIRS), bacterial sepsis, and viral sepsis, with an Area Under the Curve (AUC) larger than 0.84. Patients with a high eosinophil/B.cell.memory ratio exhibited poor survival outcomes. A total of 774 differential genes were identified in sepsis patients with a high eosinophil/B.cell.memory ratio compared to those with a low ratio. These genes were organized into seven co-expression modules associated with relevant pathways, including interferon signaling, T-cell receptor signaling, and specific granule pathways.

CONCLUSIONS

Immune cell ratios eosinophil/B.cell.memory and NK.cell.activated/NK.cell.resting in sepsis patients can be utilized for disease subtyping, prognosis, and diagnosis. The proposed cell ratios may have higher prognostic values than the neutrophil-to-lymphocyte ratio (NLR).

Persistent sepsis-induced transcriptomic signatures in signaling pathways of peripheral blood leukocytes: A pilot study

Sepsis is a dysregulated immune response to infections that frequently precipitates multiple organ dysfunction and death despite intensive supportive therapy. The aim of the present study was to identify sepsis-induced alterations in the signaling transcriptome of peripheral blood leukocytes that might shed light on the elusive transition from proinflammatory to anti-inflammatory responses and underlie long-term post-sepsis immunosuppression. Peripheral blood leukocytes were collected from subjects (i) with systemic inflammation, (ii) with sepsis in the acute phase and (iii) 6 months after recovery from sepsis, corresponding to progressive stages of the disease. Transcriptomic analysis was performed with the QuantStudio 12K Flex OpenArray Human Signal Transduction Panel analyzing transcripts of 573 genes playing a significant role in signaling. Of them, 145 genes exhibited differential expression in sepsis as compared to systemic inflammation. Pathway analysis revealed enhanced expression levels of genes involved in primary immune responses (proinflammatory cytokines, neutrophil and macrophage activation markers) and signatures characteristic of immunosuppression (increased expression of anti-inflammatory cytokines and proapoptotic genes; diminished expression of T and B cell receptor dependent activating and survival pathways). Importantly, sepsis-induced expression patterns of 39 genes were not normalized by the end of the 6-month follow-up period, indicating expression aberrations persisting long after clinical recovery. Functional analysis of these transcripts revealed downregulation of the antiapoptotic Wnt and mTOR signaling pathways that might explain the post-sepsis immunosuppression commonly seen in sepsis survivors.

The prognostic impact of SIGLEC5-induced impairment of CD8+ T cell activation in sepsis

BACKGROUND

Sepsis is associated with T-cell exhaustion, which significantly reduces patient outcomes. Therefore, targeting of immune checkpoints (ICs) is deemed necessary for effective sepsis management. Here, we evaluated the role of SIGLEC5 as an IC ligand and explored its potential as a biomarker for sepsis.

METHODS

In vitro and in vivo assays were conducted to both analyse SIGLEC5's role as an IC ligand, as well as assess its impact on survival in sepsis. A multicentre prospective cohort study was conducted to evaluate the plasmatic soluble SIGLEC5 (sSIGLEC5) as a mortality predictor in the first 60 days after admission in sepsis patients. Recruitment included sepsis patients (n = 346), controls with systemic inflammatory response syndrome (n = 80), aneurism (n = 11), stroke (n = 16), and healthy volunteers (HVs, n = 100).

FINDINGS

SIGLEC5 expression on monocytes was increased by HIF1α and was higher in septic patients than in healthy volunteers after ex vivo LPS challenge. Furthermore, SIGLEC5-PSGL1 interaction inhibited CD8+ T-cell proliferation. Administration of sSIGLEC5r (0.8 mg/kg) had adverse effects in mouse endotoxemia models. Additionally, plasma sSIGLEC5 levels of septic patients were higher than HVs and ROC analysis revealed it as a mortality marker with an AUC of 0.713 (95% CI, 0.656-0.769; p < 0.0001). Kaplan-Meier survival curve showed a significant decrease in survival above the calculated cut-off (HR of 3.418, 95% CI, 2.380-4.907, p < 0.0001 by log-rank test) estimated by Youden Index (523.6 ng/mL).

INTERPRETATION

SIGLEC5 displays the hallmarks of an IC ligand, and plasma levels of sSIGLEC5 have been linked with increased mortality in septic patients.

FUNDING

Instituto de Salud Carlos III (ISCIII) and "Fondos FEDER" to ELC (PIE15/00065, PI18/00148, PI14/01234, PI21/00869), CDF (PI21/01178), RLR (FI19/00334) and JAO (CD21/00059).

Prognostic significance of lymphocyte subpopulations for ICU-acquired infections in patients with sepsis: a retrospective study

AIM

To determine the prognostic value of lymphocyte subpopulations in predicting intensive care unit (ICU)-acquired infections among patients admitted to the ICU with sepsis.

METHODS

Data on peripheral blood lymphocyte subpopulations [CD3+ T cells, CD4+ T cells, CD8+ T cells, CD16+CD56+ natural killer (NK) cells and CD19+ B cells] were collected continuously from 188 patients admitted to the study ICUs with sepsis between January 2021 and October 2022. Clinical data collected from these patients, including medical history, number of organ failures, severity of illness scores, and characteristics of ICU-acquired infections, were reviewed.

RESULTS

Lymphocyte subpopulation counts were significantly lower in patients who acquired an infection in the ICU compared with those who did not. Univariate analyses showed that the number of organ failures [odds ratio (OR) 3.37, 95% confidence interval (CI) 2.25-5.05], severity of illness scores [Sequential Organ Failure Assessment score - OR 1.69, 95% CI 1.41-2.02; Acute Physiology and Chronic Health Evaluation II score - OR 1.26, 95% CI 0.17-1.36], history of immunosuppressant use (OR 2.41, 95% CI 1.01-5.73) and lymphocyte subpopulations (CD3+ T cells - OR 0.60, 95% CI 0.51-0.71; CD4+ T cells - OR 0.51, 95% CI 0.41-0.63; CD8+ T cells - OR 0.32, 95% CI 0.22-0.47; CD16/CD56+ NK cells - OR 0.41, 95% CI 0.28-0.59; CD19+B cells - OR 0.52, 95% CI 0.37-0.75) were associated with ICU-acquired infections. Multi-factor logistic regression analysis demonstrated that APACHE II score (OR 1.25, 95% CI 1.13-1.38), CD3+ T cells (OR 0.66, 95% CI 0.54-0.81) and CD4+ T cells (OR 0.64, 95% CI 0.50-0.82) were independent significant risk factors for ICU-acquired infections.

CONCLUSION

Assessing CD3+ T cells and CD4+ T cells within 24 h of ICU admission may help in identification of patients at risk for developing ICU-acquired infections.

Sepsis leads to lasting changes in phenotype and function of naïve CD8 T cells

Sepsis, an amplified immune response to systemic infection, is characterized by a transient cytokine storm followed by chronic immune dysfunction. Consequently, sepsis survivors are highly susceptible to newly introduced infections, suggesting sepsis can influence the function and composition of the naïve CD8 T cell pool and resulting pathogen-induced primary CD8 T cell responses. Here, we explored the extent to which sepsis induces phenotypic and functional changes within the naïve CD8 T cell pool. To interrogate this, the cecal ligation and puncture (CLP) mouse model of polymicrobial sepsis was used. In normal, non-septic mice, we show type-I interferon (IFN I)-mediated signaling plays an important role in driving the phenotypic and functional heterogeneity in the naïve CD8 T cell compartment leading to increased representation of Ly6C+ naïve CD8 T cells. In response to viral infection after sepsis resolution, naïve Ly6C+ CD8 T cells generated more primary effector and memory CD8 T cells with slower conversion to a central memory CD8 T cell phenotype (Tcm) than Ly6C- naïve CD8 T cells. Importantly, as a potent inducer of cytokine storm and IFN I production, sepsis leads to increased representation of Ly6C+ naïve CD8 T cells that maintained their heightened ability to respond (i.e., effector and memory CD8 T cell accumulation and cytokine production) to primary LCMV infection. Lastly, longitudinal analyses of peripheral blood samples obtained from septic patients revealed profound changes in CD8 T cell subset composition and frequency compared to healthy controls. Thus, sepsis has the capacity to alter the composition of naïve CD8 T cells, directly influencing primary CD8 T cell responses to newly introduced infections.

Persistence is key: unresolved immune dysfunction is lethal in both COVID-19 and non-COVID-19 sepsis

Introduction

Severe COVID-19 and non-COVID-19 pulmonary sepsis share pathophysiological, immunological, and clinical features, suggesting that severe COVID-19 is a form of viral sepsis. Our objective was to identify shared gene expression trajectories strongly associated with eventual mortality between severe COVID-19 patients and contemporaneous non-COVID-19 sepsis patients in the intensive care unit (ICU) for potential therapeutic implications.

Methods

Whole blood was drawn from 20 COVID-19 patients and 22 non-COVID-19 adult sepsis patients at two timepoints: ICU admission and approximately a week later. RNA-Seq was performed on whole blood to identify differentially expressed genes and significantly enriched pathways. Using systems biology methods, drug candidates targeting key genes in the pathophysiology of COVID-19 and sepsis were identified.

Results

When compared to survivors, non-survivors (irrespective of COVID-19 status) had 3.6-fold more "persistent" genes (genes that stayed up/downregulated at both timepoints) (4,289 vs. 1,186 genes); these included persistently downregulated genes in T-cell signaling and persistently upregulated genes in select innate immune and metabolic pathways, indicating unresolved immune dysfunction in non-survivors, while resolution of these processes occurred in survivors. These findings of persistence were further confirmed using two publicly available datasets of COVID-19 and sepsis patients. Systems biology methods identified multiple immunomodulatory drug candidates that could target this persistent immune dysfunction, which could be repurposed for possible therapeutic use in both COVID-19 and sepsis.

Discussion

Transcriptional evidence of persistent immune dysfunction was associated with 28-day mortality in both COVID-19 and non-COVID-19 septic patients. These findings highlight the opportunity for mitigating common mechanisms of immune dysfunction with immunomodulatory therapies for both diseases.

In vitro sepsis up-regulates Nociceptin/Orphanin FQ receptor expression and function on human T- but not B-cells

BACKGROUND AND PURPOSE

In animal models of sepsis, increased activation of the Nociceptin/Orphanin FQ (N/OFQ) receptor NOP is associated with mortality and NOP antagonists improved survival. We have explored the role of the N/OFQ-NOP system in freshly isolated volunteer human B- and T-cells incubated with lipopolysaccharide (LPS) and peptidoglycan G (PepG) as a model of in vitro sepsis.

EXPERIMENTAL APPROACH

B- and T-cell NOP expression was measured using the NOP fluorescent probe N/OFQATTO594 , N/OFQ content was measured using immunofluorescence, N/OFQ release was tracked using a CHOhNOPGαiq5 biosensor assay and NOP function was measured using transwell migration and cytokine/chemokine release using a 25-plex assay format. Cells were challenged with LPS/PepG.

KEY RESULTS

CD19-positive B-cells bound N/OFQATTO594 ; they also contain N/OFQ. Stimulation with CXCL13/IL-4 increased N/OFQ release. N/OFQ trended to reduced migration to CXCL13/IL-4. Surface NOP expression was unaffected by LPS/PepG, but this treatment increased GM-CSF release in an N/OFQ sensitive manner. CD3-positive T-cells did not bind N/OFQATTO594 ; they did contain N/OFQ. Stimulation with CXCL12/IL-6 increased N/OFQ release. When incubated with LPS/PepG, NOP surface expression was induced leading to N/OFQATTO594 binding. In LPS/PepG-treated cells, N/OFQ reduced migration to CXCL12/IL-6. LPS/PepG increased GM-CSF release in an N/OFQ sensitive manner.

CONCLUSIONS AND IMPLICATIONS

We suggest both a constitutive and sepsis-inducible N/OFQ-NOP receptor autocrine regulation of B- and T-cell function, respectively. These NOP receptors variably inhibit migration and reduce GM-CSF release. These data provide mechanistic insights to the detrimental role for increased N/OFQ signalling in sepsis and suggest a potential role for NOP antagonists as treatments.

The Role of Mesenchymal Stem Cell Secretome in the Inflammatory Mediators and the Survival Rate of Rat Model of Sepsis

In sepsis, simultaneously elevated levels of pro-inflammatory cytokines and interleukin (IL)-10 indicate immune response dysregulation, increasing the mortality of the host. As mesenchymal stem cell (MSC) secretome is known to have immunomodulatory effects, we aim to assess the role of MSC secretome in the inflammatory mediators (NF-κB p65 and p50, TNF-α, IL-10) and the survival rate of a rat model of sepsis. In this study, forty-eight male Rattus norvegicus rats were divided into one sham group and three groups with sepsis induction: the control group and the sepsis-induced rat groups treated with 150 μL (T1) and 300 μL (T2) of secretome. The survival rate was observed per 6 h for 48 h and plotted using the Kaplan-Meier method. Compared to the control group, T2 showed a significant decrease in the relative expression of NF-κB and the serum TNF-α level, and a significant increase in the serum IL-10 level. Meanwhile, T1 showed a significant decrease in the serum TNF-α level compared to the control group. The Kaplan-Meier Log Rank test did not show significance in the distribution of survival between T1, T2, and the control group. However, from the 18th to the 36th hour, the survival rate of T2 was lower than the survival rate of the control group and T1, with a noticeable difference between T2 and the control group, as well as T1 at the 36th hour. At the 42nd hour, the survival rate of T2 was the same as the control group and remained lower than T1. In conclusion, MSC secretome regulated the inflammatory mediators in rat model of sepsis, with a dose of 150 μL being more effective.

Emodin protects against intestinal dysfunction and enhances survival in rat model of septic peritonitis through anti-inflammatory actions

BACKGROUND

Sepsis is a significant contributor to organ function damage or failure that results in intestinal dysfunction. Emodin (Emo) has received much attention for its notable anti-inflammatory and antibacterial properties. We aimed to explore the function of Emo on sepsis.

METHODS

Sprague Dawley (SD) rats were pretreated with 20 or 40 mg/kg of Emo, followed by using cecal ligation and perforation to establish sepsis models. Hereafter, blood glucose levels, biochemical parameters, and inflammatory cytokines were measured. Additionally, ileal myeloperoxidase (MPO) activity was also measured. Diamine oxidase (DAO) level in plasma, fluorescein isothiocyanate-dextran 40 (FD-40) level in serum, bacteria number in blood and peritoneal fluid, histopathological changes of ileum, and tight junction (TJ) protein expressions in ileum were tested to evaluate the barrier function. Furthermore, CD4+ and CD8+ T cells' percentages were evaluated by flow cytometry. Finally, rats' survival rate was calculated as live rats divided by the total number of rats.

RESULTS

Emo pretreatment not only decreased blood glucose level, but also downregulated triglyceride (TG), alanine aminotransferase (ALT), aspartate aminotransferase (AST), serum creatinine (SCr), blood urea nitrogen (BUN) contents for sepsis rats, especially for the high dose of Emo (p < .05). Furthermore, Emo inhibited MPO activity and inflammatory factor release (p < .05). Crucially, after Emo administration, the barrier function of ileum was enhanced, evidenced by the reduced DAO, FD-40 levels, decreased bacteria number, alleviated pathological damage in ileum and increased TJ protein expressions (p < .05). Rats treated with Emo exhibited increased percentages of CD8+ and CD4+ T cells (p < .05), as well as an improved survival rate.

CONCLUSION

Emo exhibited a remarkable ability to attenuate sepsis by restoring intestinal dysfunction and improving survival rates, and the mechanism was closely related to anti-inflammatory properties, which provided new solid evidence for the use of Emo in treating sepsis.

Sublethal whole-body irradiation induces permanent loss and dysfunction in pathogen-specific circulating memory CD8 T cell populations

The increasing use of nuclear energy sources inevitably raises the risk of accidental or deliberate radiation exposure and associated immune dysfunction. However, the extent to which radiation exposure impacts memory CD8 T cells, potent mediators of immunity to recurring intracellular infections and malignancies, remains understudied. Using P14 CD8 T cell chimeric mice (P14 chimeras) with an lymphocytic choriomeningitis virus (LCMV) infection model, we observed that sublethal (5Gy) whole-body irradiation (WBI) induced a rapid decline in the number of naive (TN) and P14 circulating memory CD8 T cells (TCIRCM), with the former being more susceptible to radiation-induced numeric loss. While TN cell numbers rapidly recovered, as previously described, the number of P14 TCIRCM cells remained low at least 9 mo after radiation exposure. Additionally, the remaining P14 TCIRCM in irradiated hosts exhibited an inefficient transition to a central memory (CD62L+) phenotype compared to nonirradiated P14 chimeras. WBI also resulted in long-lasting T cell intrinsic deficits in memory CD8 T cells, including diminished cytokine and chemokine production along with impaired secondary expansion upon cognate Ag reencounter. Irradiated P14 chimeras displayed significantly higher bacterial burden after challenge with Listeria monocytogenes expressing the LCMV GP33-41 epitope relative to nonirradiated controls, likely due to radiation-induced numerical and functional impairments. Taken together, our findings suggest that sublethal radiation exposure caused a long-term numerical, impaired differentiation, and functional dysregulation in preexisting TCIRCM, rendering previously protected hosts susceptible to reinfection.

Single-cell transcriptome analysis reveals the regulatory effects of artesunate on splenic immune cells in polymicrobial sepsis

Sepsis is characterized by a severe and life-threatening host immune response to polymicrobial infection accompanied by organ dysfunction. Studies on the therapeutic effect and mechanism of immunomodulatory drugs on the sepsis-induced hyperinflammatory or immunosuppression states of various immune cells remain limited. This study aimed to investigate the protective effects and underlying mechanism of artesunate (ART) on the splenic microenvironment of cecal ligation and puncture-induced sepsis model mice using single-cell RNA sequencing (scRNA-seq) and experimental validations. The scRNA-seq analysis revealed that ART inhibited the activation of pro-inflammatory macrophages recruited during sepsis. ART could restore neutrophils' chemotaxis and immune function in the septic spleen. It inhibited the activation of T regulatory cells but promoted the cytotoxic function of natural killer cells during sepsis. ART also promoted the differentiation and activity of splenic B cells in mice with sepsis. These results indicated that ART could alleviate the inflammatory and/or immunosuppressive states of various immune cells involved in sepsis to balance the immune homeostasis within the host. Overall, this study provided a comprehensive investigation of the regulatory effect of ART on the splenic microenvironment in sepsis, thus contributing to the application of ART as adjunctive therapy for the clinical treatment of sepsis.

Multiple Dosing and Preactivation of Mesenchymal Stromal Cells Enhance Efficacy in Established Pneumonia Induced by Antimicrobial-Resistant Klebsiella pneumoniae in Rodents

Antimicrobial-resistant (AMR) bacteria, such as Klebsiella species, are an increasingly common cause of hospital-acquired pneumonia, resulting in high mortality and morbidity. Harnessing the host immune response to AMR bacterial infection using mesenchymal stem cells (MSCs) is a promising approach to bypass bacterial AMR mechanisms. The administration of single doses of naïve MSCs to ARDS clinical trial patient cohorts has been shown to be safe, although efficacy is unclear. The study tested whether repeated MSC dosing and/or preactivation, would attenuate AMR Klebsiella pneumonia-induced established pneumonia. Rat models of established K. pneumoniae-induced pneumonia were randomised to receive intravenous naïve or cytomix-preactivated umbilical cord MSCs as a single dose at 24 h post pneumonia induction with or without a subsequent dose at 48 h. Physiological indices, bronchoalveolar lavage (BAL), and tissues were obtained at 72 h post pneumonia induction. A single dose of naïve MSCs was largely ineffective, whereas two doses of MSCs were effective in attenuating Klebsiella pneumosepsis, improving lung compliance and oxygenation, while reducing bacteria and injury in the lung. Cytomix-preactivated MSCs were superior to naïve MSCs. BAL neutrophil counts and activation were reduced, and apoptosis increased. MSC therapy reduced cytotoxic BAL T cells, and increased CD4+/CD8+ ratios. Systemically, granulocytes, classical monocytes, and the CD4+/CD8+ ratio were reduced, and nonclassical monocytes were increased. Repeated doses of MSCs-particularly preactivated MSCs-enhance their therapeutic potential in a clinically relevant model of established AMR K. pneumoniae-induced pneumosepsis.

[Immunomodulation by nutritional intervention in critically ill patients]

Critically ill patients often suffer from a complex and severe immunological dysfunction. The differentiation and function of human immune cells are fundamentally controlled through metabolic processes. New concepts of immunonutrition therefore try to use enteral and parenteral nutrition to positively impact on the immune function of intensive care unit patients. This review article concisely presents the currently available evidence on the commonly used isolated supplements (anti-oxidative substances, amino acids, essential fatty acids) and difficulties related to their clinical use. The second part presents new and more comprehensive concepts of immunonutrition to influence the intestinal microbiome and to modulate the macronutrient composition. Immunonutrition of critically ill patients bears enormous potential and could become a valuable clinical tool for modulation of the immunometabolism of intensive care unit patients.

Uridine Alleviates Sepsis-Induced Acute Lung Injury by Inhibiting Ferroptosis of Macrophage

Uridine metabolism is extensively reported to be involved in combating oxidative stress. Redox-imbalance-mediated ferroptosis plays a pivotal role in sepsis-induced acute lung injury (ALI). This study aims to explore the role of uridine metabolism in sepsis-induced ALI and the regulatory mechanism of uridine in ferroptosis. The Gene Expression Omnibus (GEO) datasets including lung tissues in lipopolysaccharides (LPS) -induced ALI model or human blood sample of sepsis were collected. In vivo and vitro, LPS was injected into mice or administered to THP-1 cells to generate sepsis or inflammatory models. We identified that uridine phosphorylase 1 (UPP1) was upregulated in lung tissues and septic blood samples and uridine significantly alleviated lung injury, inflammation, tissue iron level and lipid peroxidation. Nonetheless, the expression of ferroptosis biomarkers, including SLC7A11, GPX4 and HO-1, were upregulated, while lipid synthesis gene (ACSL4) expression was greatly restricted by uridine supplementation. Moreover, pretreatment of ferroptosis inducer (Erastin or Era) weakened while inhibitor (Ferrostatin-1 or Fer-1) strengthened the protective effects of uridine. Mechanistically, uridine inhibited macrophage ferroptosis by activating Nrf2 signaling pathway. In conclusion, uridine metabolism dysregulation is a novel accelerator for sepsis-induced ALI and uridine supplementation may offer a potential avenue for ameliorating sepsis-induced ALI by suppressing ferroptosis.

Organism-Wide Analysis of Sepsis Reveals Mechanisms of Systemic Inflammation

Sepsis is a systemic response to infection with life-threatening consequences. Our understanding of the impact of sepsis across organs of the body is rudimentary. Here, using mouse models of sepsis, we generate a dynamic, organism-wide map of the pathogenesis of the disease, revealing the spatiotemporal patterns of the effects of sepsis across tissues. These data revealed two interorgan mechanisms key in sepsis. First, we discover a simplifying principle in the systemic behavior of the cytokine network during sepsis, whereby a hierarchical cytokine circuit arising from the pairwise effects of TNF plus IL-18, IFN-γ, or IL-1β explains half of all the cellular effects of sepsis on 195 cell types across 9 organs. Second, we find that the secreted phospholipase PLA2G5 mediates hemolysis in blood, contributing to organ failure during sepsis. These results provide fundamental insights to help build a unifying mechanistic framework for the pathophysiological effects of sepsis on the body.

Peripheral Blood Genes Crosstalk between COVID-19 and Sepsis

Severe coronavirus disease 2019 (COVID-19) has led to a rapid increase in death rates all over the world. Sepsis is a life-threatening disease associated with a dysregulated host immune response. It has been shown that COVID-19 shares many similarities with sepsis in many aspects. However, the molecular mechanisms underlying sepsis and COVID-19 are not well understood. The aim of this study was to identify common transcriptional signatures, regulators, and pathways between COVID-19 and sepsis, which may provide a new direction for the treatment of COVID-19 and sepsis. First, COVID-19 blood gene expression profile (GSE179850) data and sepsis blood expression profile (GSE134347) data were obtained from GEO. Then, we intersected the differentially expressed genes (DEG) from these two datasets to obtain common DEGs. Finally, the common DEGs were used for functional enrichment analysis, transcription factor and miRNA prediction, pathway analysis, and candidate drug analysis. A total of 307 common DEGs were identified between the sepsis and COVID-19 datasets. Protein-protein interactions (PPIs) were constructed using the STRING database. Subsequently, hub genes were identified based on PPI networks. In addition, we performed GO functional analysis and KEGG pathway analysis of common DEGs, and found a common association between sepsis and COVID-19. Finally, we identified transcription factor-gene interaction, DEGs-miRNA co-regulatory networks, and protein-drug interaction, respectively. Through ROC analysis, we identified 10 central hub genes as potential biomarkers. In this study, we identified SARS-CoV-2 infection as a high risk factor for sepsis. Our study may provide a potential therapeutic direction for the treatment of COVID-19 patients suffering from sepsis.

Sepsis-induced changes in differentiation, maintenance, and function of memory CD8 T cell subsets

Formation of long-lasting memory lymphocytes is one of the foundational characteristics of adaptive immunity and the basis of many vaccination strategies. Following the rapid expansion and contraction of effector CD8 T cells, the surviving antigen (Ag)-specific cells give rise to the memory CD8 T cells that persist for a long time and are phenotypically and functionally distinct from their naïve counterparts. Significant heterogeneity exists within the memory CD8 T cell pool, as different subsets display distinct tissue localization preferences, cytotoxic ability, and proliferative capacity, but all memory CD8 T cells are equipped to mount an enhanced immune response upon Ag re-encounter. Memory CD8 T cells demonstrate numerical stability under homeostatic conditions, but sepsis causes a significant decline in the number of memory CD8 T cells and diminishes their Ag-dependent and -independent functions. Sepsis also rewires the transcriptional profile of memory CD8 T cells, which profoundly impacts memory CD8 T cell differentiation and, ultimately, the protective capacity of memory CD8 T cells upon subsequent stimulation. This review delves into different aspects of memory CD8 T cell subsets as well as the immediate and long-term impact of sepsis on memory CD8 T cell biology.

Inefficient Recovery of Repeatedly Stimulated Memory CD8 T Cells after Polymicrobial Sepsis Induction Leads to Changes in Memory CD8 T Cell Pool Composition

Long-lasting sepsis-induced immunoparalysis has been principally studied in primary (1°) memory CD8 T cells; however, the impact of sepsis on memory CD8 T cells with a history of repeated cognate Ag encounters is largely unknown but important in understanding the role of sepsis in shaping the pre-existing memory CD8 T cell compartment. Higher-order memory CD8 T cells are crucial in providing immunity against common pathogens that reinfect the host or are generated by repeated vaccination. In this study, we analyzed peripheral blood from septic patients and show that memory CD8 T cells with defined Ag specificity for recurring CMV infection proliferate less than bulk populations of central memory CD8 T cells. Using TCR-transgenic T cells to generate 1° and higher-order (quaternary [4°]) memory T cells within the same host, we demonstrate that the susceptibility and loss of both memory subsets are similar after sepsis induction, and sepsis diminished Ag-dependent and -independent (bystander) functions of these memory subsets equally. Both the 1° and 4° memory T cell populations proliferated in a sepsis-induced lymphopenic environment; however, due to the intrinsic differences in baseline proliferative capacity, expression of receptors (e.g., CD127/CD122), and responsiveness to homeostatic cytokines, 1° memory T cells become overrepresented over time in sepsis survivors. Finally, IL-7/anti-IL-7 mAb complex treatment early after sepsis induction preferentially rescued the proliferation and accumulation of 1° memory T cells, whereas recovery of 4° memory T cells was less pronounced. Thus, inefficient recovery of repeatedly stimulated memory cells after polymicrobial sepsis induction leads to changes in memory T cell pool composition, a notion with important implications in devising strategies to recover the number and function of pre-existing memory CD8 T cells in sepsis survivors.

Study on the correlation and clinical significance of T-lymphocyte Subsets, IL-6 and PCT in the severity of patients with sepsis

Objective

To evaluate the correlation and clinical significance of T lymphocyte subsets, IL-6 and PCT in the severity of patients with sepsis.

Methods

One-hundred and twenty patients with sepsis admitted to Baoding No.1 Central Hospital from March 05, 2021 to March 05, 2022 were selected and divided into three groups according to the severity of the disease: the sepsis group, the severe sepsis group and the septic shock group, with 40 cases in each group. The venous blood of all patients was drawn with a sterile vacuum blood collection tube after admission to detect the levels of T lymphocyte subsets CD3+, CD4+, CD8+, CD4+/CD8+, and the venous blood was collected to detect the levels of interleukin-6 (IL-6) and procalcitonin (PCT). The three groups of patients were compared to analyze whether there were differences, and whether there was a correlation between the level of each indicator and the prognosis of patients after treatment.

Results

The levels of CD3+, CD4+ and CD4+/CD8+ in the three groups decreased with the aggravation of the disease, with a significant difference (p=0.00). The levels of IL-6 and PCT increased with the aggravation of the disease among the three groups, with statistically significant differences (IL-6, p=0.00; PCT, p=0.01). The better the patients recovered after treatment, the higher the levels of CD4+ and CD4+/CD8+, and the two were positively correlated; While the lower the levels of IL-6 and PCT, the two were negatively correlated.

Conclusion

Peripheral blood T lymphocyte subsets and serum IL-6, PCT are abnormally expressed in patients with sepsis, and have a close bearing on the severity of the disease, which has a certain predictive value for patients after recovery. In view of this, the above indicators are of high clinical significance.

Sepsis: Immunopathology, Immunotherapies, and Future Perspectives

Sepsis is a syndrome that includes physiological, pathological, and biochemical abnormalities resulting from the host immune response to infection. Despite the improved treatment modalities in recent years, the incidence and mortality of sepsis are still increasing. Sepsis immunopathology is increasingly attracting the attention of researchers. The successes experienced with immunotherapeutics in the treatment of cancer and coronavirus disease 2019, which are diseases with similar pathophysiological features and common immune defects with sepsis, have given rise to the hope that similar successes can be achieved in the treatment of sepsis. In this review, future perspectives on the immunopathology of sepsis and immunotherapeutics are presented to improve the current understanding of the disease.

T cell dysregulation in inflammatory diseases in ICU

Severe inflammatory diseases, including sepsis, are characterized by an impaired host adaptive and innate immunity which results in immunosuppression, responsible for secondary infections and increased morbidity and mortality in critically ill patients. T cells are major actors of the immune system. During post-aggressive immunosuppression, lymphopenia, reduction of innate T cells, changes in T helper cell polarization and regulatory T cell increase are observed. The main mechanisms involved in T cell dysregulation are T cell apoptosis, autophagy deficiency, T cell anergy, T cell exhaustion and T cell metabolic reprogramming. In this review, we describe the alterations of T cell regulation, their mechanisms, and their association with clinical outcomes in severe inflammatory diseases, foremost of which is the sepsis.

This review focuses on the alterations of T cell regulation and their mechanisms in severe inflammatory ICU diseases. Lymphopenia, reduction of innate T cells, changes in T helper cell polarization and regulatory T cell increase contribute to secondary immunosuppression in ICU patients.

Screening of Sepsis Biomarkers Based on Bioinformatics Data Analysis

Methods

Gene expression profiles of GSE13904, GSE26378, GSE26440, GSE65682, and GSE69528 were obtained from the National Center for Biotechnology Information (NCBI). The differentially expressed genes (DEGs) were searched using limma software package. Gene Ontology (GO) functional analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and protein-protein interaction (PPI) network analysis were performed to elucidate molecular mechanisms of DEGs and screen hub genes.

Results

A total of 108 DEGs were identified in the study, of which 67 were upregulated and 41 were downregulated. 15 superlative diagnostic biomarkers (CCL5, CCR7, CD2, CD27, CD274, CD3D, GNLY, GZMA, GZMH, GZMK, IL2RB, IL7R, ITK, KLRB1, and PRF1) for sepsis were identified by bioinformatics analysis.

Conclusion

15 hub genes (CCL5, CCR7, CD2, CD27, CD274, CD3D, GNLY, GZMA, GZMH, GZMK, IL2RB, IL7R, ITK, KLRB1, and PRF1) have been elucidated in this study, and these biomarkers may be helpful in the diagnosis and therapy of patients with sepsis.

Inflammation Controls Susceptibility of Immune-Experienced Mice to Sepsis

Sepsis, an amplified immune response to systemic infection that leads to life-threatening organ dysfunction, affects >125,000 people/day worldwide with 20% mortality. Modest therapeutic progress for sepsis has been made, in part because of the lack of therapeutic translatability between mouse-based experimental models and humans. One potential reason for this difference stems from the extensive use of immunologically naive specific pathogen-free mice in preclinical research. To address this issue, we used sequential infections with well-defined BSL-2 pathogens to establish a novel immune-experienced mouse model (specific pathogen experienced [SPexp]) to determine the extent to which immunological experience and/or inflammation influences the host capacity to respond to subsequent infections, including sepsis. Consistent with their immunological experience, SPexp inbred or outbred mice had significant changes in the composition and activation status of multiple leukocyte populations known to influence the severity of cecal ligation and puncture-induced sepsis. Importantly, by varying the timing of sepsis induction, we found the level of basal inflammation controls sepsis-induced morbidity and mortality in SPexp mice. In addition, although a beneficial role of NK cells in sepsis was recently demonstrated in specific pathogen-free mice, NK cell depletion before cecal ligation and puncture induction in SPexp mice lead to diminished mortality, suggesting NK cells may have beneficial or detrimental roles in the response to septic insult dependent on host immune status. Thus, data highlight the importance of utilizing immune-experienced models for preclinical studies to interrogate the cellular/molecular mechanism(s) that could be therapeutically exploited during severe and dysregulated infection-induced inflammatory responses, such as sepsis.