Association of monocyte HLA-DR expression over time with secondary infection in critically ill children: a prospective observational study

Causal relationships between immune cells, inflammatory cytokines, and pertussis: Bidirectional 2-sample Mendelian randomization study and mediation analysis

Studies have shown that immune cells play an important role in the occurrence and development of pertussis, but the specific causal relationships are yet to be determined. Additionally, inflammatory cytokines, as regulators of immune responses, may mediate the relationship between immune cells and pertussis, and the specific mechanisms involved require further exploration. This study utilizes data from multiple large-scale genome-wide association studies, covering 731 types of immune cells and 91 types of inflammatory cytokines. The bidirectional 2-sample Mendelian randomization (MR) method is employed, with inverse-variance weighted as the main statistical approach, to assess the causal relationships between immune cells, inflammatory cytokines, and pertussis. Furthermore, a 2-step MR method is used to investigate the mediating role of inflammatory cytokines in the effect of immune cells on pertussis. Our study results indicate that 11 types of immune cells have a protective effect against pertussis, with the strongest protection observed from CD25 on CD28+ CD4+ cells (OR = 0.3533, CI = 0.1636-0.7627, P = .008). Conversely, 19 types of immune cells are positively associated with the risk of pertussis, with the strongest correlation found in CD3- lymphocyte %lymphocyte (OR = 3.6613, CI = 1.5012-8.299, P = .0043). Additionally, 3 inflammatory cytokines - IL-4, IL-18R1, and FGF-21 - show a causal relationship with pertussis. Our mediation MR results indicate that inflammatory cytokines do not act as mediators in the relationship between immune cells and pertussis. This study suggests a causal relationship between immune cells and pertussis, while inflammatory cytokines do not appear to be mediating factors in the pathway from immune cells to pertussis.

Decreased monocytic HLA-DR in patients with sepsis: Prediction of diagnosis, severity and prognosis

OBJECTIVE

Sepsis is characterized by high incidence and mortality rates, making early recognition and risk stratification critical for preventing delayed treatment and overtreatment. This study investigated the potential of monocytic (m) HLA-DR as a diagnostic and prognostic biomarker of sepsis.

METHODS

In this prospective study, we collected blood in EDTA-anticoagulated tubes within 48 h from patients diagnosed with sepsis or infection and analyzed the percentage of mHLA-DR in peripheral blood mononuclear cells, C-reactive protein, and procalcitonin within 2 h of collection. We gathered clinical and laboratory data, including sex, age, and comorbidities, calculated the number of dysfunctional organs and sequential organ failure assessment (SOFA) score, and recorded the survival status of patients with sepsis on the 30th day after admission.

RESULTS

mHLA-DR levels were lower in patients with sepsis (median 46.60 [interquartile range 23.86-66.51]%) than infection (75.44 [52.13-91.50]%). mHLA-DR could distinguish sepsis from infection with an area under the curve (AUC) of 0.724 (95 %CI 0.624-0.824). Decreased mHLA-DR levels have been found in septic patients with shock or secondary infections. mHLA-DR expression decreased with an increasing number of dysfunctional organs and higher SOFA score. In 30-day non-survivors, mHLA-DR levels were 26.94 (12.06-44.45)%, significantly lower than in survivors (55.20 [24.83-72.37]%). mHLA-DR predicted sepsis prognosis with an AUC of 0.750 (95 %CI 0.623-0.877). When the cut-off value was <52.29 %, the sensitivity and specificity of mHLA-DR for prognosis were 100 % and 52.83 %, respectively. The 30-day survival rate of septic patients with mHLA-DR ≥ 52.29 % was 6.798 (95 %CI 2.075-22.27) times higher than that of patients with mHLA-DR < 52.29 %.

CONCLUSION

mHLA-DR negatively correlates with the severity of sepsis and could be used as a diagnostic and prognostic biomarker for sepsis.

Immunotherapy in the context of sepsis-induced immunological dysregulation

Sepsis is a clinical syndrome caused by uncontrollable immune dysregulation triggered by pathogen infection, characterized by high incidence, mortality rates, and disease burden. Current treatments primarily focus on symptomatic relief, lacking specific therapeutic interventions. The core mechanism of sepsis is believed to be an imbalance in the host's immune response, characterized by early excessive inflammation followed by late immune suppression, triggered by pathogen invasion. This suggests that we can develop immunotherapeutic treatment strategies by targeting and modulating the components and immunological functions of the host's innate and adaptive immune systems. Therefore, this paper reviews the mechanisms of immune dysregulation in sepsis and, based on this foundation, discusses the current state of immunotherapy applications in sepsis animal models and clinical trials.

Utility of monocyte HLA-DR and rationale for therapeutic GM-CSF in sepsis immunoparalysis

Sepsis, a heterogeneous clinical syndrome, features a systemic inflammatory response to tissue injury or infection, followed by a state of reduced immune responsiveness. Measurable alterations occur in both the innate and adaptive immune systems. Immunoparalysis, an immunosuppressed state, associates with worsened outcomes, including multiple organ dysfunction syndrome, secondary infections, and increased mortality. Multiple immune markers to identify sepsis immunoparalysis have been proposed, and some might offer clinical utility. Sepsis immunoparalysis is characterized by reduced lymphocyte numbers and downregulation of class II human leukocyte antigens (HLA) on innate immune monocytes. Class II HLA proteins present peptide antigens for recognition by and activation of antigen-specific T lymphocytes. One monocyte class II protein, mHLA-DR, can be measured by flow cytometry. Downregulated mHLA-DR indicates reduced monocyte responsiveness, as measured by ex-vivo cytokine production in response to endotoxin stimulation. Our literature survey reveals low mHLA-DR expression on peripheral blood monocytes correlates with increased risks for infection and death. For mHLA-DR, 15,000 antibodies/cell appears clinically acceptable as the lower limit of immunocompetence. Values less than 15,000 antibodies/cell are correlated with sepsis severity; and values at or less than 8000 antibodies/cell are identified as severe immunoparalysis. Several experimental immunotherapies have been evaluated for reversal of sepsis immunoparalysis. In particular, sargramostim, a recombinant human granulocyte-macrophage colony-stimulating factor (rhu GM-CSF), has demonstrated clinical benefit by reducing hospitalization duration and lowering secondary infection risk. Lowered infection risk correlates with increased mHLA-DR expression on peripheral blood monocytes in these patients. Although mHLA-DR has shown promising utility for identifying sepsis immunoparalysis, absence of a standardized, analytically validated method has thus far prevented widespread adoption. A clinically useful approach for patient inclusion and identification of clinically correlated output parameters could address the persistent high unmet medical need for effective targeted therapies in sepsis.