Infection-induced changes in hematopoiesis

Macrophage memories of early-life injury drive neonatal nociceptive priming

The developing peripheral nervous and immune systems are functionally distinct from those of adults. These systems are vulnerable to early-life injury, which influences outcomes related to nociception following subsequent injury later in life (i.e., "neonatal nociceptive priming"). The underpinnings of this phenomenon are unclear, although previous work indicates that macrophages are trained by inflammation and injury. Our findings show that macrophages are both necessary and partially sufficient to drive neonatal nociceptive priming, possibly due to a long-lasting remodeling in chromatin structure. The p75 neurotrophic factor receptor is an important effector in regulating neonatal nociceptive priming through modulation of the inflammatory profile of rodent and human macrophages. This "pain memory" is long lasting in females and can be transferred to a naive host to alter sex-specific pain-related behaviors. This study reveals a mechanism by which acute, neonatal post-surgical pain drives a peripheral immune-related predisposition to persistent pain following a subsequent injury.

Aryl hydrocarbon receptor activation alters immune cell populations in the lung and bone marrow during coronavirus infection

Respiratory viral infections are one of the major causes of illness and death worldwide. Symptoms associated with respiratory infections can range from mild to severe, and there is limited understanding of why there is large variation in severity. Environmental exposures are a potential causative factor. The aryl hydrocarbon receptor (AHR) is an environment-sensing molecule expressed in all immune cells. Although there is considerable evidence that AHR signaling influences immune responses to other immune challenges, including respiratory pathogens, less is known about the impact of AHR signaling on immune responses during coronavirus (CoV) infection. In this study, we report that AHR activation significantly altered immune cells in the lungs and bone marrow of mice infected with a mouse CoV. AHR activation transiently reduced the frequency of multiple cells in the mononuclear phagocyte system, including monocytes, interstitial macrophages, and dendritic cells in the lung. In the bone marrow, AHR activation altered myelopoiesis, as evidenced by a reduction in granulocyte-monocyte progenitor cells and an increased frequency of myeloid-biased progenitor cells. Moreover, AHR activation significantly affected multiple stages of the megakaryocyte lineage. Overall, these findings indicate that AHR activation modulates multiple aspects of the immune response to a CoV infection. Given the significant burden of respiratory viruses on human health, understanding how environmental exposures shape immune responses to infection advances our knowledge of factors that contribute to variability in disease severity and provides insight into novel approaches to prevent or treat disease.NEW & NOTEWORTHY Our study reveals a multifaceted role for aryl hydrocarbon receptor (AHR) signaling in the immune response to coronavirus (CoV) infection. Sustained AHR activation during in vivo mouse CoV infection altered the frequency of mature immune cells in the lung and modulated emergency hematopoiesis, specifically myelopoiesis and megakaryopoiesis, in bone marrow. This provides new insight into immunoregulation by the AHR and extends our understanding of how environmental exposures can impact host responses to respiratory viral infections.

Macrophage epigenetic memories of early life injury drive neonatal nociceptive priming

The developing peripheral nervous and immune systems are functionally distinct from adults. These systems are vulnerable to early life injury, which influences outcomes related to nociception following subsequent injury later in life (neonatal nociceptive priming). The underpinnings of this phenomenon are largely unknown, although previous work indicates that macrophages are epigenetically trained by inflammation and injury. We found that macrophages are both necessary and partially sufficient to drive neonatal nociceptive priming possibly due to a long-lasting epigenetic remodeling. The p75 neurotrophic factor receptor (NTR) was an important effector in regulating neonatal nociceptive priming through modulation of the inflammatory profile of rodent and human macrophages. This pain memory was long lasting in females and could be transferred to a naive host to alter sex-specific pain-related behaviors. This study reveals a novel mechanism by which acute, neonatal post-surgical pain drives a peripheral immune-related predisposition to persistent pain following a subsequent injury.

Developmental impact of peripheral injury on neuroimmune signaling

A peripheral injury drives neuroimmune interactions at the level of the injury and throughout the neuraxis. Understanding these systems will be beneficial in the pursuit to target persistent pain that involves both neural and immune components. In this review, we discuss the impact of injury on the development of neuroimmune signaling, along with data that suggest a possible cellular immune memory. We also discuss the parallel effects of injury in the nervous system and immune related areas including bone marrow, lymph node and central nervous system-related cells. Finally, we relate these findings to patient populations and current research that evaluates human tissue.

Bone Marrow Changes in Septic Shock: A Comprehensive Review

Septic shock is a life-threatening condition characterized by systemic inflammation resulting from a severe infection. Although the primary focus of sepsis research has traditionally been on the dysfunctional immune response, recent studies have highlighted the important role of bone marrow in the pathophysiology of septic shock. The bone marrow, traditionally regarded as the hematopoietic organ responsible for blood cell production, undergoes significant changes during sepsis, contributing to the overall immune dysregulation observed in this condition. This comprehensive review aims to provide a detailed overview of the bone marrow changes associated with septic shock. It explores the alterations in the bone marrow microenvironment, hematopoietic progenitor cells, and the subsequent effects on leukocyte production and function. Key cellular and molecular mechanisms involved in bone marrow dysfunction during septic shock are discussed, including the dysregulation of cytokines, chemokines, growth factors, and signaling pathways. Furthermore, this review highlights the clinical implications of bone marrow changes in septic shock. It emphasizes the impact of altered hematopoiesis on immune cell populations, such as neutrophils, monocytes, and lymphocytes, and their role in the progression and outcome of sepsis. The potential prognostic value of bone marrow parameters and the therapeutic implications of targeting bone marrow dysfunction are also addressed. The review summarizes relevant preclinical and clinical studies to comprehensively understand the current knowledge of bone marrow changes in septic shock. The limitations and challenges of studying bone marrow in the context of sepsis are acknowledged, and future directions for research are proposed.

Innate activation of human neutrophils and neutrophil-like cells by the pro-inflammatory bacterial metabolite ADP-heptose and Helicobacter pylori

Lipopolysaccharide inner core heptose metabolites, including ADP-heptose, play a substantial role in the activation of cell-autonomous innate immune responses in eukaryotic cells, via the ALPK1-TIFA signaling pathway, as demonstrated for various pathogenic bacteria. The important role of LPS heptose metabolites during Helicobacter pylori infection of the human gastric niche has been demonstrated for gastric epithelial cells and macrophages, while the role of heptose metabolites on human neutrophils has not been investigated. In this study, we aimed to gain a better understanding of the activation potential of bacterial heptose metabolites for human neutrophil cells. To do so, we used pure ADP-heptose and, as a bacterial model, H. pylori, which can transport heptose metabolites into the human host cell via the Cag Type 4 Secretion System (CagT4SS). Main questions were how bacterial heptose metabolites impact on the pro-inflammatory activation, alone and in the bacterial context, and how they influence maturation of human neutrophils. Results of the present study demonstrated that neutrophils respond with high sensitivity to pure heptose metabolites, and that global regulation networks and neutrophil maturation are influenced by heptose exposure. Furthermore, activation of human neutrophils by live H. pylori is strongly impacted by the presence of LPS heptose metabolites and the functionality of its CagT4SS. Similar activities were determined in cell culture neutrophils of different maturation states and in human primary neutrophils. In conclusion, we demonstrated that specific heptose metabolites or bacteria producing heptoses exhibit a strong activity on cell-autonomous innate responses of human neutrophils.

Chronic LCMV infection regulates the effector T cell response by inducing the generation of less immunogenic dendritic cells

Chronic viral infection impairs systemic immunity in the host; however, the mechanism underlying the dysfunction of immune cells in chronic viral infection is incompletely understood. In this study, we studied the lineage differentiation of hematopoietic stem cells (HSCs) during chronic viral infection to elucidate the changes in dendritic cell (DC) differentiation and subsequent impact on T cell functionality using a chronic lymphocytic choriomeningitis virus (LCMV) infection model. We first investigated the lineage differentiation of HSCs in the bone marrow (BM) to elucidate the modulation of immune cell differentiation and found that the populations highly restrained in their differentiation were common myeloid progenitors (CMPs) and common dendritic cell progenitors (CDPs). Of interest, the main immune cells infected with LCMV Clone 13 (CL13) in the BM were CD11b/c⁺ myeloid DCs. We next characterized CD11b⁺ DCs that differentiated during chronic LCMV infection. These DCs displayed a less immunogenic phenotype than DCs in naive or acutely infected mice, showing low expression of CD80 but high expression of PD-L1, B7-H4, IDO, TGF-β, and IL-10. Consequently, these CD11b⁺ DCs induced less effective CD8⁺ T cells and more Foxp3⁺ regulatory T (Treg) cells. Furthermore, CD11b⁺ DCs generated during CL13 infection could not induce effective CD8⁺ T cells specific to the antigens of newly invading pathogens. Our findings demonstrate that DCs generated from the BM during chronic viral infection cannot activate fully functional effector CD8⁺ T cells specific to newly incoming antigens as well as persistent antigens themselves, suggesting a potential cause of the functional alterations in the T cell immune response during chronic viral infection.

The wild mouse bone marrow has a unique myeloid and lymphoid composition and phenotype

The murine bone marrow has a central role in immune function and health as the primary source of leukocytes in adult mice. Laboratory mice provide a human-homologous, genetically manipulable and reproducible model that has enabled an immeasurable volume of high-quality immunological research. However, recent research has questioned the translatability of laboratory mouse research into humans and proposed that the exposure of mice to their wild and natural environment may hold the key to further immunological breakthroughs. To date, there have been no studies providing an in-depth cellular analysis of the wild mouse bone marrow. This study utilized wild mice from an isolated island population (Isle of May, Scotland, UK) and performed flow cytometric and histological analysis to characterize the myeloid, lymphoid, hematopoietic progenitor, and adipocyte compartments within the wild mouse bone marrow. We find that, compared to laboratory mouse bone marrow, the wild mouse bone marrow differs in every cell type assessed. Some of the major distinctions include; a smaller B cell compartment with an enriched presence of plasma cells, increased proportions of KLRG1+ CD8+ T cells, diminished CD11b expression in the myeloid lineage and a five-fold enlargement of the eosinophil compartment. We conclude that the wild mouse bone marrow is dramatically distinct from its laboratory counterparts, with multiple phenotypes that to our knowledge have never been observed in laboratory models. Further research into these unique features may uncover novel immunological mechanisms and grant a greater understanding of the role of the immune system in a natural setting.

Pharmacological Evaluation of the Anesthetic and Analgesic Potential of Injection Harsha 22: A Novel Polyherbal Local Anesthetic Formulation Intended for Parenteral Administration in Wistar Albino Rats

Background

Local anaesthetics are medications that cause numbness that can be reversed by applying them topically. Local anaesthetics are clinically used to control pain during minor surgeries or to treat other acute and chronic pain. The present investigation intended to investigate the anesthetic as well as analgesic potential of Injection Harsha 22, a novel polyherbal formulation in Wistar albino rats.

Methods

The anesthetic potential of Injection Harsha 22 was evaluated by a heat tail-flick latency (TFL) test, whereas the analgesic effect was elevated by electrical stimulation testing. Here, lignocaine (2%) was used as the standard anesthetic drug.

Results

In TFL, Injection Harsha 22 showed anesthetic effects up to 90 minutes after application. Also, the duration of anesthesia in rats that were administered subcutaneously with Injection Harsha 22 was comparable to that of the rats treated with commercial lignocaine (2%). In an electrical stimulation test, single administration of Injection Harsha 22 to rats significantly prolonged analgesia compared with the normal control group. The median duration of analgesia in rats administered subcutaneously with Injection Harsha 22 and lignocaine solution was 40 minutes and 35 minutes, respectively. Furthermore, Injection Harsha 22 does not interfere with the hematopoietic system of the experiment animals.

Conclusion

Thus, the present investigation established the in vivo anesthetic and analgesic potential of Injection Harsha 22 in experimental animals. Hence, it can be concluded that Injection Harsha 22 can become a prominent substitute for lignocaine as a local anaesthetic agent after establishing its efficacy through stringent clinical trials in humans.

Myeloid-like B cells boost emergency myelopoiesis through IL-10 production during infection

Emergency myelopoiesis (EM) is a hematopoietic response against systemic infections that quickly supplies innate immune cells. As lymphopoiesis is strongly suppressed during EM, the role of lymphocytes in that process has not received much attention. Here, we found that myeloid-like B cells (M-B cells), which express myeloid markers, emerge in the bone marrow (BM) after the induction of EM. M-B cells were mainly derived from pre-B cells and preferentially expressed IL-10, which directly stimulates hematopoietic progenitors to enhance their survival and myeloid-biased differentiation. Indeed, lacking IL-10 in B cells, blocking IL-10 in the BM with a neutralizing antibody, and deleting the IL-10 receptor in hematopoietic progenitors significantly suppressed EM, which failed to clear microbes in a cecal ligation and puncture model. Thus, a distinct B cell subset generated during infection plays a pivotal role in boosting EM, which suggests the on-demand reinforcement of EM by adaptive immune cells.

Royal Jelly Increases Hematopoietic Stem Cells in Peripheral Blood: A Double-Blind, Placebo-Controlled, Randomized Trial in Healthy Subjects

Objectives

Royal jelly (RJ), produced by honeybees, influences stem cell functions, such as pluripotency maintenance of mouse embryonic stem cells and prevention of aging-related muscle stem cell functional deterioration. Thus, we hypothesized that RJ administration has various health-promoting effects based on stem cells. However, its effects are unknown in humans. In this study, we have attempted for the first time to clarify whether the administration of RJ in humans affects stem cells.

Materials and Methods

This randomized, double-blind, placebo-controlled study was performed on healthy subjects (n = 90) who received protease-treated RJ at a dose of 1200 mg/day or placebo daily for four weeks. Also, the participants with a low number of hematopoietic stem cells (HSCs) in peripheral blood were preferentially selected. HSC counts, endothelial progenitor cell (EPC) counts, blood cell counts in peripheral blood, cytokines in serum, and physical conditions were evaluated. Results and Conclusion. Eligible data from 86 subjects (placebo: 42, RJ: 44) who completed the study were analyzed. There were no significant differences between the two groups regarding the changes in peripheral HSC count (p=0.103), while diastolic blood pressure showed a significant improvement in the RJ group compared to that in the placebo group (p=0.032). The subgroup analysis excluded 14 subjects who complained of cold symptoms at baseline or within five days of the four-week study. The changes in the HSC populations were significantly higher in the RJ group than those in the placebo group (p=0.042). No adverse effects were observed in any of the groups. These results suggest that RJ administration affected the peripheral HSC count and may influence stem cell functions. Further research is needed to reveal the various health-promoting benefits of RJ based on stem cells.

HSC-derived fatty acid oxidation in steady-state and stressed hematopoiesis

Metabolism impacts all cellular functions and plays a fundamental role in physiology. Metabolic regulation of hematopoiesis is dynamically regulated under steady-state and stress conditions. It is clear that hematopoietic stem cells (HSCs) impose different energy demands and flexibility during maintenance compared with stressed conditions. However, the cellular and molecular mechanisms underlying metabolic regulation in HSCs remain poorly understood. In this review, we focus on defining the role of fatty acid oxidation (FAO) in HSCs. We first review the existing literature describing FAO in HSCs under steady-state hematopoiesis. Next, we describe the models used to examine HSCs under stress conditions, and, finally, we describe how infection causes a shift toward FAO in HSCs and the impact of using this pathway on emergency hematopoiesis.

Immunopathology of chronic critical illness in sepsis survivors: Role of abnormal myelopoiesis

Sepsis remains the single most common cause of mortality and morbidity in hospitalized patients requiring intensive care. Although earlier detection and improved treatment bundles have reduced in-hospital mortality, long-term recovery remains dismal. Sepsis survivors who experience chronic critical illness often demonstrate persistent inflammation, immune suppression, lean tissue wasting, and physical and functional cognitive declines, which often last in excess of 1 year. Older patients and those with preexisting comorbidities may never fully recover and have increased mortality compared with individuals who restore their immunologic homeostasis. Many of these responses are shared with individuals with advanced cancer, active autoimmune diseases, chronic obstructive pulmonary disease, and chronic renal disease. Here, we propose that this resulting immunologic endotype is secondary to a persistent maladaptive reprioritization of myelopoiesis and pathologic activation of myeloid cells. Driven in part by the continuing release of endogenous alarmins from chronic organ injury and muscle wasting, as well as by secondary opportunistic infections, ongoing myelopoiesis at the expense of lymphopoiesis and erythropoiesis leads to anemia, recurring infections, and lean tissue wasting. Early recognition and intervention are required to interrupt this pathologic activation of myeloid populations.

You are what you eat: How to best fuel your immune system

Normal bone marrow (BM) homeostasis ensures consistent production of progenitor cells and mature blood cells. This requires a reliable supply of nutrients in particular free fatty acids, carbohydrates and protein. Furthermore, rapid changes can occur in response to stress such as infection which can alter the demand for each of these metabolites. In response to infection the haematopoietic stem cells (HSCs) must respond and expand rapidly to facilitate the process of emergency granulopoiesis required for the immediate immune response. This involves a shift from the use of glycolysis to oxidative phosphorylation for energy production and therefore an increased demand for metabolites. Thus, the right balance of each dietary component helps to maintain not only normal homeostasis but also the ability to quickly respond to systemic stress. In addition, some dietary components can drive chronic inflammatory changes in the absence of infection or immune stress, which in turn can impact on overall immune function. The optimal nutrition for the best immunological outcomes would therefore be a diet that supports the functions of immune cells allowing them to initiate effective responses against pathogens but also to resolve the response rapidly when necessary and to avoid any underlying chronic inflammation. In this review we discuss how these key dietary components can alter immune function, what is their impact on bone marrow metabolism and how changes in dietary intake of each of these can improve the outcomes of infections.

Alignment of single-cell trajectories by tuMap enables high-resolution quantitative comparison of cancer samples

Single-cell technologies allow characterization of cancer samples as continuous developmental trajectories. Yet, the obtained temporal resolution cannot be leveraged for a comparative analysis due to the large phenotypic heterogeneity existing between patients. Here, we present the tuMap algorithm that exploits high-dimensional single-cell data of cancer samples exhibiting an underlying developmental structure to align them with the healthy development, yielding the tuMap pseudotime axis that allows their systematic, meaningful comparison. We applied tuMap on single-cell mass cytometry data of acute lymphoblastic and myeloid leukemia to reveal associations between the tuMap pseudotime axis and clinics that outperform cellular assignment into developmental populations. Application of the tuMap algorithm on single-cell RNA sequencing data further identified gene signatures of stem cells residing at the very-early parts of the cancer trajectories. The quantitative framework provided by tuMap allows generation of metrics for cancer patients evaluation.

Remodeling of the Bone Marrow Stromal Microenvironment During Pathogenic Infections

The bone marrow (BM) is the primary hematopoietic organ and a hub in which organismal demands for blood cellular output are systematically monitored. BM tissues are additionally home to a plethora of mature immune cell types, providing functional environments for the activation of immune responses and acting as preferred anatomical reservoirs for cells involved in immunological memory. Stromal cells of the BM microenvironment crucially govern different aspects of organ function, by structuring tissue microanatomy and by directly providing essential regulatory cues to hematopoietic and immune components in distinct niches. Emerging evidence demonstrates that stromal networks are endowed with remarkable functional and structural plasticity. Stress-induced adaptations of stromal cells translate into demand-driven hematopoiesis. Furthermore, aberrations of stromal integrity arising from pathological conditions critically contribute to the dysregulation of BM function. Here, we summarize our current understanding of the alterations that pathogenic infections and ensuing inflammatory conditions elicit on the global topography of the BM microenvironment, the integrity of anatomical niches and cellular interactions, and ultimately, on the regulatory function of diverse stromal subsets.

Mitochondria and the Tumour Microenvironment in Blood Cancer

The bone marrow (BM) is a complex organ located within the cavities of bones. The main function of the BM is to produce all the blood cells required for a normal healthy blood system. As with any major organ, many diseases can arise from errors in bone marrow function, including non-malignant disorders such as anaemia and malignant disorders such as leukaemias. This article will explore the role of the bone marrow, in normal and diseased haematopoiesis, with an emphasis on the requirement for intercellular mitochondrial transfer in leukaemia.

Trained Immunity as an Adaptive Branch of Innate Immunity

The concept of trained immunity has become one of the most interesting and potentially commercially and clinically relevant ideas of current immunology. Trained immunity is realized by the epigenetic reprogramming of non-immunocompetent cells, primarily monocytes/macrophages and natural killer (NK) cells, and is less specific than adaptive immunity; therefore, it may cross-protect against other infectious agents. It remains possible, however, that some of the observed changes are simply caused by increased levels of immune reactions resulting from supplementation with immunomodulators, such as glucan. In addition, the question of whether we can talk about trained immunity in cells with a life span of only few days is still unresolved.

Long-term impact of congenital toxoplasmosis on phenotypic and functional features of circulating leukocytes from infants one year after treatment onset

Changes in immune response of children with congenital toxoplasmosis (CT) regarding infection evolution and therapeutic intervention was addressed. Infants with CT presented increased counts of monocytes, CD3^-CD16^-CD56^High, CD3⁺CD56⁺ and CD4⁺ T-cells 1-year after treatment onset (TOXO_1-yearAT). Smaller numbers of CD3^-CD16^-CD56⁺ and TCRγδ⁺ T-cells were specifically observed in infants with retinochoroidal lesions (L(+)). When infants were classified based on the baseline status, expansion of CD3^-CD16^-CD56^High and CD4⁺ T-cells were observed in L(+) who had active, active/cicatricial or cicatricial lesions. Infants who had active or active/cicatricial lesions display augmented numbers of monocytes, CD3^-CD16⁺CD56⁺, CD3⁺CD56⁺, CD8⁺DR⁺ and TCRγδ⁺ T-cells and those with active/cicatricial or cicatricial at baseline displayed increase in CD14⁺CD64⁺ monocytes. Moreover, all L(+) had increased IFN-γ⁺ and IL-10⁺ CD4⁺ T-cells, while L(-) had increased ratios of TNF⁺, IFN-γ⁺ and IL-4⁺ NK-cells upon antigen-specific stimulation. Persistent alterations in leukocytes in TOXO_1-yearAT suggest long-term sequels in the immune system of infants with CT.

Lymphopenia Caused by Virus Infections and the Mechanisms Beyond

Viral infections can give rise to a systemic decrease in the total number of lymphocytes in the blood, referred to as lymphopenia. Lymphopenia may affect the host adaptive immune responses and impact the clinical course of acute viral infections. Detailed knowledge on how viruses induce lymphopenia would provide valuable information into the pathogenesis of viral infections and potential therapeutic targeting. In this review, the current progress of viruses-induced lymphopenia is summarized and the potential mechanisms and factors involved are discussed.

Myeloid-Derived Suppressor Cells in Trypanosoma cruzi Infection

Myeloid-derived suppressor cells (MDSCs) are immature heterogeneous myeloid cells that expand in pathologic conditions as cancer, trauma, and infection. Although characterization of MDSCs is continuously revisited, the best feature is their suppressor activity. There are many markers for MDSC identification, it is distinctive that they express inducible nitric oxide synthase (iNOS) and arginase 1, which can mediate immune suppression. MDSCs can have a medullary origin as a result of emergency myelopoiesis, but also can have an extramedullary origin. Early studies on Trypanosoma cruzi infection showed severe immunosuppression, and several mechanisms involving parasite antigens and host cell mediators were described as inhibition of IL-2 and IL-2R. Another mechanism of immunosuppression involving tumor necrosis factor/interferon γ-dependent nitric oxide production by inducible nitric oxide synthase was also described. Moreover, other studies showed that nitric oxide was produced by CD11b⁺ Gr-1⁺ MDSCs in the spleen, and later iNOS and arginase 1 expressed in CD11b⁺Ly6C⁺Ly6G^lo monocytic MDSC were found in spleen and heart of T. cruzi infected mice that suppressed T cell proliferation. Uncontrolled expansion of monocytic MDSCs leads to L-arginine depletion which hinders nitric oxide production leading to death. Supplement of L-arginine partially reverts L-arginine depletion and survival, suggesting that L-arginine could be administered along with anti-parasitical drugs. On the other hand, pharmacological inhibition of MDSCs leads to death in mice, suggesting that some expansion of MDSCs is needed for an efficient immune response. The role of signaling molecules mediating immune suppression as reactive oxygen species, reactive nitrogen species, as well as prostaglandin E2, characteristics of MDSCs, in T. cruzi infection is not fully understood. We review and discuss the role of these reactive species mediators produced by MDSCs. Finally, we discuss the latest results that link the SLAMF1 immune receptor with reactive oxygen species. Interaction of the parasite with the SLAMF1 modulates parasite virulence through myeloid cell infectivity and reactive oxygen species production. We discuss the possible strategies for targeting MDSCs and SLAMF1 receptor in acute Trypanosoma cruzi infection in mice, to evaluate a possible translational application in human acute infections.

The monocyte-to-lymphocyte ratio: Sex-specific differences in the tuberculosis disease spectrum, diagnostic indices and defining normal ranges

Background

The monocyte-to-lymphocyte ratio (MLR) has been advocated as a biomarker in tuberculosis. Our objective was to evaluate its clinical value and associations.

Methods

Blood counts, inflammatory markers and clinical parameters were measured in patients with and those screened for tuberculosis. Complete blood counts (CBCs) from a multi-ethnic population aged 16 to 65 years were evaluated; a sub-group with normal hematological indices was used to define the range of MLRs.

Results

Multivariate analysis in proven tuberculosis (n = 264) indicated MLR associated with low serum albumin, high white cell counts and a positive culture; values were higher in sputum smear-positive pulmonary tuberculosis (S+PTB). Analysis in S+PTB (n = 296) showed higher MLRs in males and those with high neutrophil counts, low serum albumin and high C-reactive protein. The diagnostic value of MLRs was assessed by comparing notified patients with TB (n = 264) with denotified cases (n = 50), active case-finding in non-contacts (TB n = 111 and LTBI n = 373) and contacts of S+PTB (n = 149) with S+PTB found at screening (n = 75). Sensitivities and specificities ranged from 58.0–62.5% and 50.0–70.0% respectively for optimal cut-off values, defined by ROC curves. In CBCs obtained over one month, ratios correlated with neutrophil counts (ρ = 0.48, P<0.00001, n = 14,573; MLR = 0.45 at 8–8.9 x 10⁹/L) and were higher in males than females (P<0.0001). The MLR range (mean ± 2SD) in those with normal hematological indices (n = 3921: females 0.122–0.474; males 0.136–0.505) paralleled LTBI MLRs. Ratios did not predict death (n = 29) nor response to treatment (n = 178 S+PTB with follow-up CBCs). Ratios were higher in males than female in the 16–45 years age group, where immune differences due to sex hormones are likely greatest.

Conclusions

Severe tuberculosis and male sex associated with high MLRs; the same variables likely affect the performance of other biomarkers. The ratio performed poorly as a clinical aid.

Sclerostin Depletion Induces Inflammation in the Bone Marrow of Mice

Romosozumab, a humanized monoclonal antibody specific for sclerostin (SOST), has been approved for treatment of postmenopausal women with osteoporosis at a high risk for fracture. Previous work in sclerostin global knockout (Sost^-/-) mice indicated alterations in immune cell development in the bone marrow (BM), which could be a possible side effect in romosozumab-treated patients. Here, we examined the effects of short-term sclerostin depletion in the BM on hematopoiesis in young mice receiving sclerostin antibody (Scl-Ab) treatment for 6 weeks, and the effects of long-term Sost deficiency on wild-type (WT) long-term hematopoietic stem cells transplanted into older cohorts of Sost^-/- mice. Our analyses revealed an increased frequency of granulocytes in the BM of Scl-Ab-treated mice and WT→Sost^-/- chimeras, indicating myeloid-biased differentiation in Sost-deficient BM microenvironments. This myeloid bias extended to extramedullary hematopoiesis in the spleen and was correlated with an increase in inflammatory cytokines TNFα, IL-1α, and MCP-1 in Sost^-/- BM serum. Additionally, we observed alterations in erythrocyte differentiation in the BM and spleen of Sost^-/- mice. Taken together, our current study indicates novel roles for Sost in the regulation of myelopoiesis and control of inflammation in the BM.

Myelopoiesis of acute inflammation: lessons from TGN1412-induced cytokine storm

TGN1412, a superagonist monoclonal antibody targeting CD28, caused cytokine storm in six healthy volunteers in a first-in-man study in 2006. Despite clinical improvement and termination of the cytokine release syndrome within days, anemia persisted in all patients with hemoglobin reaching baseline levels as much as 6 months later. Granulocytic dysplasia continued for 20 days in association with increased expression of CD69 and IL-4, but reduced IL-10; with resolution, this profile reversed to higher IL-10 expression and counter-balanced circannual cycling of IL-4 and IL-10 thereafter over 7 months. Along with immune cell subset and cytokine correlates monitored over 2 years, these observations offer unique insights into the expected changes in myelopoiesis and natural resolution in otherwise healthy young individuals in response to acute inflammation and cytokine storm in the absence of concomitant infection or comorbidity.

Innate Immune Memory in Hematopoietic Stem/Progenitor Cells: Myeloid-Biased Differentiation and the Role of Interferon

Innate immune memory was first described for monocytes and other myeloid cells. This memory is designated Immune Training, in which the host animals that had experienced pathogen infection earlier acquire improved resistance to a second infection. Innate immune memory is mediated by an epigenetic mechanism traced to transcriptional memory that is conserved throughout evolution and has been selected for the ability to mount an adaptive response to shifting environments. Accumulating evidence shows that not only peripheral myeloid cells but hematopoietic stem/progenitor cells (HSCs/HSPCs) can acquire epigenetic memory upon pathogen exposure. Systemic pathogen infection causes HSCs to exit from quiescence and facilitate myeloid-biased differentiation that leads to efficient host defense. This sequence of events is common in HSC memory generation, which is triggered by different stimuli. Recent studies show that not only pathogens but other stimuli such as metabolic stress can generate memory in HSCs. This review summarizes recent publications relevant to HSC memory. We discuss the current understanding of initial sensors, soluble mediators/cytokines involved in memory formation, including Type I and Type II interferons along with future implications.

CD86-based analysis enables observation of bona fide hematopoietic responses

Hematopoiesis is a system that provides red blood cells (RBCs), leukocytes, and platelets, which are essential for oxygen transport, biodefense, and hemostasis; its balance thus affects the outcome of various disorders. Here, we report that stem cell antigen-1 (Sca-1), a cell surface marker commonly used for the identification of multipotent hematopoietic progenitors (Lin-Sca-1+c-Kit+ cells; LSKs), is not suitable for the analysis of hematopoietic responses under biological stresses with interferon production. Lin-Sca-1-c-Kit+ cells (LKs), downstream progenitors of LSKs, acquire Sca-1 expression upon inflammation, which makes it impossible to distinguish between LSKs and LKs. As an alternative and stable marker even under such stresses, we identified CD86 by screening 180 surface markers. The analysis of infection/inflammation-triggered hematopoiesis on the basis of CD86 expression newly revealed urgent erythropoiesis producing stress-resistant RBCs and intact reconstitution capacity of LSKs, which could not be detected by conventional Sca-1-based analysis.

The spleen: "epicenter" in malaria infection and immunity

The spleen is a complex secondary lymphoid organ that plays a crucial role in controlling blood‐stage infection with Plasmodium parasites. It is tasked with sensing and removing parasitized RBCs, erythropoiesis, the activation and differentiation of adaptive immune cells, and the development of protective immunity, all in the face of an intense inflammatory environment. This paper describes how these processes are regulated following infection and recognizes the gaps in our current knowledge, highlighting recent insights from human infections and mouse models.

The Role of the Bone Marrow Microenvironment in the Response to Infection

Hematopoiesis in the bone marrow (BM) is the primary source of immune cells. Hematopoiesis is regulated by a diverse cellular microenvironment that supports stepwise differentiation of multipotent stem cells and progenitors into mature blood cells. Blood cell production is not static and the bone marrow has evolved to sense and respond to infection by rapidly generating immune cells that are quickly released into the circulation to replenish those that are consumed in the periphery. Unfortunately, infection also has deleterious effects injuring hematopoietic stem cells (HSC), inefficient hematopoiesis, and remodeling and destruction of the microenvironment. Despite its central role in immunity, the role of the microenvironment in the response to infection has not been systematically investigated. Here we summarize the key experimental evidence demonstrating a critical role of the bone marrow microenvironment in orchestrating the bone marrow response to infection and discuss areas of future research.

Impact of bacterial infections on erythropoiesis

INTRODUCTION

The importance of iron is highlighted by the many complex metabolic pathways in which it is involved. A sufficient supply is essential for the effective production of 200 billion erythrocytes daily, a process called erythropoiesis.

AREAS COVERED

During infection, the human body can withhold iron from pathogens, mechanism termed nutritional immunity. The subsequent disturbances in iron homeostasis not only impact on immune function and infection control, but also negatively affect erythropoiesis. The complex interplay between iron, immunity, erythropoiesis and infection control on the molecular and clinical level are highlighted in this review. Diagnostic algorithms for correct interpretation and diagnosis of the iron status in the setting of infection are presented. Therapeutic concepts are discussed regarding effects on anemia correction, but also toward their role on the course of infection.

EXPERT OPINION

In the setting of infection, anemia is often neglected and its impact on the course of diseases is incompletely understood. Clinical expertise can be improved in correct diagnosing of anemia and disturbances of iron homeostasis. Systemic studies are needed to evaluate the impact of specific therapeutic interventions on anemia correction on the course of infection, but also on patients' cardiovascular performance and quality of life.

Airways exposure of bacterial superantigen SEB enhances bone marrow eosinophil population and facilitates its egress to blood and lung tissue

BACKGROUND

Differentiation of bone marrow eosinophils (BM-EO) and its trafficking to peripheral blood and respiratory mucosa are a hallmark of inflammatory diseases. Staphylococcal enterotoxin B (SEB) has been shown to aggravate airways eosinophilic inflammation. This study aimed to investigate the effects of mouse airways SEB exposure on BM-EO population, as well as its adhesive properties and release of cytokines/chemokines that orchestrate BM-EO trafficking to lungs.

METHODS

Male BALB/c mice were intranasally exposed to SEB (1 μg), and at 4, 16, 24 and 48 h thereafter, bone marrow (BM), circulating blood and bronchoalveolar lavage (BAL) fluid were collected. Levels of cytokines/chemokines and expressions of VLA-4 and CCR3 in BM were evaluated. Adhesion of BM to ICAM-1 and VCAM-1 were also evaluated.

RESULTS

SEB exposure promoted a marked eosinophil influx to BAL at 16 and 24 h after exposure, which was accompanied by significant increases in counts of immature (16 h) and mature (4 to 48 h) forms of eosinophil in BM, along with blood eosinophilia (16 h). In BM, higher levels of eotaxin, IL-5, IL-4, IL-3 and IL-7 were detected at 16 to 48 h. SEB also significantly increased CCR3 expression and calcium levels in BM-EO, and enhanced the cell adhesion to ICAM-1 (24 h) and ICAM-1 (48 h).

CONCLUSION

Airways SEB exposure increases the number of eosinophils in BM by mechanisms involving a network of cytokine and chemokine release, facilitating the BM-EO adhesion to ICAM-1 and VCAM-1 to gain access to the peripheral blood and lung tissues.

Clinical implications of increased uptake in bone marrow and spleen on FDG-PET in patients with bacteremia

PURPOSE

To investigate which clinical factors and laboratory values are associated with high FDG uptake in the bone marrow and spleen on 2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography (PET)/computed tomography (CT) in patients with bacteremia.

METHODS

One hundred forty-five consecutive retrospective patients with bacteremia who underwent FDG-PET/CT between 2010 and 2017 were included. Mean standard uptake values (SUV_mean) of FDG in bone marrow, liver, and spleen were measured. Bone marrow-to-liver SUV ratios (BLR) and spleen-to-liver SUV ratios (SLR) were calculated. Linear regression analyses were performed to examine the association of BLR and SLR with age, gender, hemoglobin, leukocyte count, platelets, glucose level, C-reactive protein (CRP), microorganism, days of antibiotic treatment before FDG-PET/CT, infection focus, use of immunosuppressive drugs, duration of hospital stay (after FDG-PET/CT), ICU admission, and mortality.

RESULTS

C-reactive protein (p = 0.006), a cardiovascular or musculoskeletal focus of infection (p = 0.000 for both), and bacteremia caused by Gram-negative bacteria (p = 0.002) were independently and positively associated with BLR, while age (p = 0.000) and glucose level before FDG-PET/CT (p = 0.004) were independently and negatively associated with BLR. For SLR, CRP (p = 0.001) and a cardiovascular focus of infection (p = 0.020) were independently and positively associated with SLR, while age (p = 0.002) and glucose level before FDG-PET/CT (p = 0.016) were independently and negatively associated with SLR.

CONCLUSION

High FDG uptake in the bone marrow is associated with a higher inflammatory response and younger age in patients with bacteremia. In patients with high FDG uptake in the bone marrow, a cardiovascular or musculoskeletal focus of infection is more likely than other foci, and the infection is more often caused by Gram-negative species. High splenic FDG uptake is associated with a higher inflammatory response as well, and a cardiovascular focus of infection is also more likely in case of high splenic FDG uptake.

Bacteria-Induced Acute Inflammation Does Not Reduce the Long-Term Reconstitution Capacity of Bone Marrow Hematopoietic Stem Cells

Pathogen-initiated chronic inflammation or autoimmune diseases accelerate proliferation and promote differentiation of hematopoietic stem cells (HSCs) but simultaneously reduce reconstitution capacity. Nevertheless, the effect of acute infection and inflammation on functional HSCs is still largely unknown. Here we found that acute infection elicited by heat-inactivated Escherichia coli (HIEC) expanded bone marrow lineage-negative (Lin)⁻ stem-cell antigen 1 (Sca-1)⁺cKit⁺ (LSK) cell population, leading to reduced frequency of functional HSCs in LSK population. However, the total number of BM phenotypic HSCs (Flk2⁻CD48⁻CD150⁺ LSK cells) was not altered in HIEC-challenged mice. Additionally, the reconstitution capacity of the total BM between infected and uninfected mice was similar by both the competitive repopulation assay and measurement of functional HSCs by limiting dilution. Thus, occasionally occurring acute inflammation, which is critical for host defenses, is unlikely to affect HSC self-renewal and maintenance of long-term reconstitution capacity. During acute bacterial infection and inflammation, the hematopoietic system can replenish hematopoietic cells consumed in the innate inflammatory response by accelerating hematopoietic stem and progenitor cell proliferation, but preserving functional HSCs in the BM.

Acute Plasmodium berghei Mouse Infection Elicits Perturbed Erythropoiesis With Features That Overlap With Anemia of Chronic Disease

Severe malaria anemia is one of the most common causes of morbidity and mortality arising from infection with Plasmodium falciparum. The pathogenesis of malarial anemia is complex, involving both parasite and host factors. As mouse models of malaria also develop anemia, they can provide a useful resource to study the impact of Plasmodium infections and the resulting host innate immune response on erythropoiesis. In this study, we have characterized the bone marrow and splenic responses of the erythroid as well as other hematopoietic lineages after an acute infection of Balb/c mice with Plasmodium berghei. Such characterization of the hematopoietic changes is critical to underpin future studies, using knockout mice and transgenic parasites, to tease out the interplay between host genes and parasite modulators implicated in susceptibility to malaria anemia. P. berghei infection led to a clear perturbation of steady-state erythropoiesis, with the most profound defects in polychromatic and orthochromatic erythroblasts as well as erythroid colony- and burst-forming units (CFU-E and BFU-E), resulting in an inability to compensate for anemia. The perturbation in erythropoiesis was not attributable to parasites infecting erythroblasts and affecting differentiation, nor to insufficient erythropoietin (EPO) production or impaired activation of the Signal transducer and activator of transcription 5 (STAT5) downstream of the EPO receptor, indicating EPO-signaling remained functional in anemia. Instead, the results point to acute anemia in P. berghei-infected mice arising from increased myeloid cell production in order to clear the infection, and the concomitant release of pro-inflammatory cytokines and chemokines from myeloid cells that inhibit erythroid development, in a manner that resembles the pathophysiology of anemia of chronic disease.

The role of macrophages in protective and pathological responses to Toxoplasma gondii

The ability of Toxoplasma gondii to cause clinical disease in immune-competent and immune-deficient hosts coupled with its ease of use in vitro and availability of murine models has led to its use as a model organism to study how the immune system controls an intracellular infection. This article reviews the studies that established the role of the cytokine IFN-γ in the activation of macrophages to control T gondii and the events that lead to the mobilization and expansion of macrophage populations and their ability to limit parasite replication. Macrophages also have pro-inflammatory functions that promote protective NK and T-cell activities as well as regulatory properties that facilitate the resolution of inflammation. Nevertheless, while macrophages are important in determining the outcome of infection, T gondii has evolved mechanisms to subvert macrophage activation and can utilize their migratory activities to promote dissemination and these two properties underlie the ability of this parasite to persist and cause disease.

Exploring Phenotypes for Disease Resilience in Pigs Using Complete Blood Count Data From a Natural Disease Challenge Model

Disease resilience is a valuable trait to help manage infectious diseases in livestock. It is anticipated that improved disease resilience will sustainably increase production efficiency, as resilient animals maintain their performance in the face of infection. The objective of this study was to identify phenotypes related to disease resilience using complete blood count (CBC) data from a wean-to-finish natural disease challenge model, established to mimic the disease pressure caused by many common pathogens at the commercial level of pig production. In total, 2433 F1 crossbred (Landrace × Yorkshire) barrows that went through the natural disease challenge model were classified into four groups (resilient, average, susceptible, and dead) based on their divergent responses in terms of growth and individual treatment. Three sets of blood samples for CBC analysis were drawn at 2-weeks before, and at 2- and 6-weeks after the challenge: Blood 1, Blood 3, and Blood 4 respectively. CBC of Blood 1 taken from healthy pigs before challenge did not show differences between groups. However, resilient animals were found to be primed to initiate a faster adaptive immune response and recover earlier following infection, with greater increases of lymphocyte concentration from Blood 1 to Blood 3 and for hemoglobin concentration and hematocrit from Blood 3 to Blood 4, but a lower neutrophil concentration from Blood 3 to Blood 4 than in susceptible and dead animals (FDR < 0.05). The CBC traits in response to the challenge were found to be heritable and genetically correlated with growth and treatment, which may indicate the potential for developing CBC under disease or commercial conditions as a phenotype in commercial systems as part of developing predictions for disease resilience.

The stage-specific impairment of granulopoiesis in people living with HIV/AIDS (PLWHA) with neutropenia

Neutropenia and impaired functions were common manifestation in antiretroviral therapy (ART) in both naïve and experienced PLWHA. Granulopoiesis can be divided into two phases: lineage determination and committed granulopoiesis. However, stage-specific impairment of granulopoiesis in PLWHA with neutropenia remains unclear. A total of 48 ART-naïve and 49 ART-experienced PLWHA from 2016 to 2018 were recruited and divided into non-, mild-, and moderate-to-severe-neutropenia groups according to their neutrophil counts. The bone marrow aspirates and peripheral blood were collected and analyzed by multicolor flow cytometry for granulocyte subsets, hematopoietic stem/progenitor cells (HSPC), apoptosis, and emigration and retention of different subsets. Compared with healthy donors, the percentages of circulating segmented neutrophils were significantly decreased along with an increase of immature neutrophils in both groups. ART-naïve patients with moderate to severe neutropenia exhibited decreased proportion and accelerated apoptosis of relative mature segmented neutrophils. In contrast, ART-experienced patients with neutropenia displayed decreased proportion of granulocyte macrophage progenitors, indicating a defect at a stage of lineage determination. Meanwhile, ART-experienced patients with neutropenia also the expression of CXCR4 segmented neutrophils, suggesting an increased retention of segmented neutrophils inn the bone marrow. ART-naïve patients with neutropenia is caused by increased apoptosis of relatively differentiated neutrophils at committed granulopoiesis, whereas impaired lineage determination and enhanced retention of segmented neutrophils contribute to in ART-experienced patients.

Role of growth factors in hematopoietic stem cell niche

Hematopoietic stem cells (HSCs) produce new blood cells everyday throughout life, which is maintained by the self-renewal and differentiation ability of HSCs. This is not controlled by the HSCs alone, but rather by the complex and exquisite microenvironment surrounding the HSCs, which is called the bone marrow niche and consists of various bone marrow cells, growth factors, and cytokines. It is essential to understand the characteristic role of the stem cell niche and the growth factors in the niche formation. In this review, we describe the role of the bone marrow niche and factors for niche homeostasis, and also summarize the latest research related to stem cell niche.

Airway exposure to Staphylococcal enterotoxin type B (SEB) enhances the number and activity of bone marrow neutrophils via the release of multiple cytokines

BACKGROUND

The lung infections by Staphylococcus aureus are strongly associated with its ability to produce enterotoxins. However, little is known about the mechanisms underlying trafficking of bone marrow (BM) neutrophils during airway inflammation induced by Staphylococcal enterotoxin B (SEB). We therefore aimed to investigate the effects of mouse airways SEB exposure on BM neutrophil counts and its adhesive properties as well as on the release of cytokines/chemokines that orchestrate BM neutrophils trafficking to lung tissue.

METHODS

Male BALB/c mice were intranasally exposed to SEB (1 µg), and at 4, 16 and 24 h thereafter, BM, circulating blood, bronchoalveolar lavage (BAL) fluid and lung tissue were collected. BM neutrophils adhesion, MAC-1 and LFA1-α expressions (by flow cytometry) as well as measurement of cytokine and/or chemokines levels were assayed after SEB-airway exposure.

RESULTS

Prior exposure to SEB promoted a marked influx of neutrophils to BAL and lung tissue, which was accompanied by increased counts of BM immature neutrophils and blood neutrophilia. BM neutrophil expressions of LFA1-α and MAC-1 were unchanged by SEB exposure whereas a significant enhancement of adhesion properties to VCAM-1 was observed. The early phase of airway SEB exposure was accompanied by high levels of GM-CSF, G-CSF, IFN-γ, TNF-α and KC/CXCL1, while the latter phase by the equilibrated actions of SDF1-α and MIP-2.

CONCLUSION

Mouse airways exposure to SEB induces BM cytokines/chemokines release and their integrated actions enhance the adhesion of BM neutrophils leading to acute lung injury.

IL-27 receptor-regulated stress myelopoiesis drives abdominal aortic aneurysm development

Abdominal aortic aneurysm (AAA) is a prevalent life-threatening disease, where aortic wall degradation is mediated by accumulated immune cells. Although cytokines regulate inflammation within the aorta, their contribution to AAA via distant alterations, particularly in the control of hematopoietic stem cell (HSC) differentiation, remains poorly defined. Here we report a pathogenic role for the interleukin-27 receptor (IL-27R) in AAA, as genetic ablation of IL-27R protects mice from the disease development. Mitigation of AAA is associated with a blunted accumulation of myeloid cells in the aorta due to the attenuation of Angiotensin II (Ang II)-induced HSC expansion. IL-27R signaling is required to induce transcriptional programming to overcome HSC quiescence and increase differentiation and output of mature myeloid cells in response to stress stimuli to promote their accumulation in the diseased aorta. Overall, our studies illuminate how a prominent vascular disease can be distantly driven by a cytokine-dependent regulation of bone marrow precursors.

To be red or white: lineage commitment and maintenance of the hematopoietic system by the "inner myeloid"

Differentiation of hematopoietic stem and progenitor cells is tightly regulated depending on environmental changes in order to maintain homeostasis. Transcription factors direct the development of hematopoietic cells, such as GATA-1 for erythropoiesis and PU.1 for myelopoiesis. However, recent findings obtained from single-cell analyses raise the question of whether these transcription factors are "initiators" or just "executors" of differentiation, leaving the initiation of hematopoietic stem and progenitor cell differentiation (i.e. lineage commitment) unclear. While a stochastic process is likely involved in commitment, it cannot fully explain the homeostasis of hematopoiesis nor "on-demand" hematopoiesis in response to environmental changes. Transcription factors BACH1 and BACH2 may regulate both commitment and on-demand hematopoiesis because they control erythroid-myeloid and lymphoid-myeloid differentiation by repressing the myeloid program, and their activities are repressed in response to infectious and inflammatory conditions. We summarize possible mechanisms of lineage commitment of hematopoietic stem and progenitor cells suggested by recent findings and discuss the erythroid and lymphoid commitment of hematopoietic stem and progenitor cells, focusing on the gene regulatory network composed of genes encoding key transcription factors. Surprising similarity exists between commitment to erythroid and lymphoid lineages, including repression of the myeloid program by BACH factors. The suggested gene regulatory network of BACH factors sheds light on the myeloid-based model of hematopoiesis. This model will help to understand the tuning of hematopoiesis in higher eukaryotes in the steady-state condition as well as in emergency conditions, the evolutional history of the system, aging and hematopoietic disorders.

Myeloid and CD4 T Cells Comprise the Latent Reservoir in Antiretroviral Therapy-Suppressed SIVmac251-Infected Macaques

Human immunodeficiency virus (HIV) eradication or long-term suppression in the absence of antiretroviral therapy (ART) requires an understanding of all viral reservoirs that could contribute to viral rebound after ART interruption. CD4 T cells (CD4s) are recognized as the predominant reservoir in HIV type 1 (HIV-1)-infected individuals. However, macrophages are also infected by HIV-1 and simian immunodeficiency virus (SIV) during acute infection and may persist throughout ART, contributing to the size of the latent reservoir. We sought to determine whether tissue macrophages contribute to the SIVmac251 reservoir in suppressed macaques. Using cell-specific quantitative viral outgrowth assays (CD4-QVOA and MΦ-QVOA), we measured functional latent reservoirs in CD4s and macrophages in ART-suppressed SIVmac251-infected macaques. Spleen, lung, and brain in all suppressed animals contained latently infected macrophages, undetectable or low-level SIV RNA, and detectable SIV DNA. Silent viral genomes with potential for reactivation and viral spread were also identified in blood monocytes, although these cells might not be considered reservoirs due to their short life span. Additionally, virus produced in the MΦ-QVOA was capable of infecting healthy activated CD4s. Our results strongly suggest that functional latent reservoirs in CD4s and macrophages can contribute to viral rebound and reestablishment of productive infection after ART interruption. These findings should be considered in the design and implementation of future HIV cure strategies.IMPORTANCE This study provides further evidence that the latent reservoir is comprised of both CD4+ T cells and myeloid cells. The data presented here suggest that CD4+ T cells and macrophages found throughout tissues in the body can contain replication-competent SIV and contribute to rebound of the virus after treatment interruption. Additionally, we have shown that monocytes in blood contain latent virus and, though not considered a reservoir themselves due to their short life span, could contribute to the size of the latent reservoir upon entering the tissue and differentiating into long-lived macrophages. These new insights into the size and location of the SIV reservoir using a model that is heavily studied in the HIV field could have great implications for HIV-infected individuals and should be taken into consideration with the development of future HIV cure strategies.

Monocyte-Derived Dendritic Cells Dictate the Memory Differentiation of CD8+ T Cells During Acute Infection

Monocyte-derived dendritic cells (moDCs) have been shown to robustly expand during infection; however, their roles in anti-infectious immunity remain unclear. Here, we found that moDCs were dramatically increased in the secondary lymphoid organs during acute LCMV infection in an interferon-γ (IFN-γ)-dependent manner. We also found that priming by moDCs enhanced the differentiation of memory CD8⁺ T cells compared to differentiation primed by conventional dendritic cells (cDCs) through upregulation of Eomesodermin (Eomes) and T cell factor-1 (TCF-1) expression in CD8⁺ T cells. Consequently, impaired memory formation of CD8⁺ T cells in mice that had reduced numbers of moDCs led to defective clearance of pathogens upon rechallenge. Mechanistically, attenuated interleukin-2 (IL-2) signaling in CD8⁺ T cells primed by moDCs was responsible for the enhanced memory programming of CD8⁺ T cells. Therefore, our findings unveil a specialization of the antigen-presenting cell subsets in the fate determination of CD8⁺ T cells during infection and pave the way for the development of a novel therapeutic intervention on infection.

The Fluctuations of Leukocytes and Circulating Cytokines in Septic Humanized Mice Vary With Outcome

Sepsis remains a major challenge in translational research given its heterogeneous pathophysiology and the lack of specific therapeutics. The use of humanized mouse chimeras with transplanted human hematopoietic cells may improve the clinical relevance of pre-clinical studies. However, knowledge of the human immuno-inflammatory response during sepsis in humanized mice is scarce; it is unclear how similar or divergent mouse and human-origin immuno-inflammatory responses in sepsis are. In this study, we evaluated the early outcome-dependent immuno-inflammatory response in humanized mice generated in the NSG strain after cecal ligation and puncture (CLP) sepsis. Mice were observed for 32 h post-CLP and were assigned to either predicted-to-die (P-DIE) or predicted-to-survive (P-SUR) groups for retrospective comparisons. Blood samples were collected at baseline, 6 and 24 h, whereas the bone marrow and spleen were collected between 24 and 32 h post-CLP. In comparison to P-SUR, P-DIE humanized mice had a 3-fold higher frequency of human splenic monocytes and their CD80 expression was reduced by 1.3-fold; there was no difference in the HLA-DR expression. Similarly, the expression of CD80 on the bone marrow monocytes from P-DIE mice was decreased by 32% (p < 0.05). Sepsis induced a generalized up-regulation of both human and murine plasma cytokines (TNFα, IL-6, IL-10, IL-8/KC, MCP-1); it was additionally aggravated in P-DIE vs. P-SUR. Human cytokines were strongly overridden by the murine ones (approx. ratio 1:9) but human TNFα was 7-fold higher than mouse TNFα. Interestingly, transplantation of human cells did not influence murine cytokine response in NSG mice, but humanized NSG mice were more susceptible to sepsis in comparison with NSG mice (79 vs. 33% mortality; p < 0.05). In conclusion, our results show that humanized mice reflect selected aspects of human immune responses in sepsis and therefore may be a feasible alternative in preclinical immunotherapy modeling.

Hematopoietic Stem Cell Heterogeneity

Hematopoietic stem cells (HSCs) maintain lifelong production of mature blood cells and regenerate the hematopoietic system after cytotoxic injury. Use of expanding cell surface marker panels and advanced functional analyses have revealed the presence of several immunophenotypically different HSC subsets with distinct self-renewal and repopulating capacity and bias toward selective lineage differentiation. This chapter summarizes current understanding of the phenotypic and functional heterogeneity within the HSC pool, with emphasis on the immunophenotypes and functional features of several known HSC subsets, and their roles in steady-state and emergency hematopoiesis, and in aging. The chapter also highlights some of the future research directions to elucidate further the biology and function of different HSC subsets in health and disease states.

Telomere length measurement by qPCR - Summary of critical factors and recommendations for assay design

Research in the last decade has explored the length of telomeres, the protective ends of eukaryotic chromosomes, as a biomarker for the cumulative effects of environmental exposures and life experiences as well as a risk factor for major diseases. With a growing interest in telomere biology across biomedical, epidemiological and public health research, it is critical to ensure that the measurement of telomere length is performed with high precision and accuracy. Of the several major methods utilized to determine telomere length, quantitative PCR (qPCR) remains the most cost-effective and suitable method for large-scale epidemiological and population studies. However, inconsistencies in recent reports utilizing the qPCR method highlight the need for a careful methodological analysis of each step of this process. In this review, we summarize each critical step in qPCR telomere length assay, including sample type selection, sample collection, storage, processing issues and assay procedures. We provide guidance and recommendations for each step based on current knowledge. It is clear that a collaborative and rigorous effort is needed to characterize and resolve existing issues related to sample storage, both before and after DNA extraction, as well as the impact of different extraction protocols, reagents and post extraction processing across all tissue types (e.g. blood, saliva, buccal swabs, etc.) to provide the needed data upon which best practices for TL analyses can be agreed upon. Additionally, we suggest that the whole telomere research community be invited to collaborate on the development and implementation of standardized protocols for the assay itself as well as for reporting in scientific journals. The existing evidence provides substantial support for the continuation of telomere research across a range of different exposures and health outcomes. However, as with any technological or methodologic advance in science, reproducibility, reliability and rigor need to be established to ensure the highest quality research.

Bordetella pertussis Whole Cell Immunization, Unlike Acellular Immunization, Mimics Naïve Infection by Driving Hematopoietic Stem and Progenitor Cell Expansion in Mice

Hematopoietic stem and progenitor cell (HSPC) compartments are altered to direct immune responses to infection. Their roles during immunization are not well-described. To elucidate mechanisms for waning immunity following immunization with acellular vaccines (ACVs) against Bordetella pertussis (Bp), we tested the hypothesis that immunization with Bp ACVs and whole cell vaccines (WCVs) differ in directing the HSPC characteristics and immune cell development patterns that ultimately contribute to the types and quantities of cells produced to fight infection. Our data demonstrate that compared to control and ACV-immunized CD-1 mice, immunization with an efficacious WCV drives expansion of hematopoietic multipotent progenitor cells (MPPs), increases circulating white blood cells (WBCs), and alters the size and composition of lymphoid organs. In addition to MPPs, common lymphoid progenitor (CLP) proportions increase in the bone marrow of WCV-immunized mice, while B220⁺ cell proportions decrease. Upon subsequent infection, increases in maturing B cell populations are striking in WCV-immunized mice. RNAseq analyses of HSPCs revealed that WCV and ACV-immunized mice vastly differ in developing VDJ gene segment diversity. Moreover, gene set enrichment analyses demonstrate WCV-immunized mice exhibit unique gene signatures that suggest roles for interferon (IFN) induced gene expression. Also observed in naïve infection, these IFN stimulated gene (ISG) signatures point toward roles in cell survival, cell cycle, autophagy, and antigen processing and presentation. Taken together, these findings underscore the impact of vaccine antigen and adjuvant content on skewing and/or priming HSPC populations for immune response.

EVI1 overexpression reprograms hematopoiesis via upregulation of Spi1 transcription

Inv(3q26) and t(3:3)(q21;q26) are specific to poor-prognosis myeloid malignancies, and result in marked overexpression of EVI1, a zinc-finger transcription factor and myeloid-specific oncoprotein. Despite extensive study, the mechanism by which EVI1 contributes to myeloid malignancy remains unclear. Here we describe a new mouse model that mimics the transcriptional effects of 3q26 rearrangement. We show that EVI1 overexpression causes global distortion of hematopoiesis, with suppression of erythropoiesis and lymphopoiesis, and marked premalignant expansion of myelopoiesis that eventually results in leukemic transformation. We show that myeloid skewing is dependent on DNA binding by EVI1, which upregulates Spi1, encoding master myeloid regulator PU.1. We show that EVI1 binds to the -14 kb upstream regulatory element (-14kbURE) at Spi1; knockdown of Spi1 dampens the myeloid skewing. Furthermore, deletion of the -14kbURE at Spi1 abrogates the effects of EVI1 on hematopoietic stem cells. These findings support a novel mechanism of leukemogenesis through EVI1 overexpression.

Infection perturbs Bach2- and Bach1-dependent erythroid lineage 'choice' to cause anemia

Elucidation of how the differentiation of hematopoietic stem and progenitor cells (HSPCs) is reconfigured in response to the environment is critical for understanding the biology and disorder of hematopoiesis. Here we found that the transcription factors (TFs) Bach2 and Bach1 promoted erythropoiesis by regulating heme metabolism in committed erythroid cells to sustain erythroblast maturation and by reinforcing erythroid commitment at the erythro-myeloid bifurcation step. Bach TFs repressed expression of the gene encoding the transcription factor C/EBPβ, as well as that of its target genes encoding molecules important for myelopoiesis and inflammation; they achieved the latter by binding to their regulatory regions also bound by C/EBPβ. Lipopolysaccharide diminished the expression of Bach TFs in progenitor cells and promoted myeloid differentiation. Overexpression of Bach2 in HSPCs promoted erythroid development and inhibited myelopoiesis. Knockdown of BACH1 or BACH2 in human CD34⁺ HSPCs impaired erythroid differentiation in vitro. Thus, Bach TFs accelerate erythroid commitment by suppressing the myeloid program at steady state. Anemia of inflammation and myelodysplastic syndrome might involve reduced activity of Bach TFs.

Extravascular coagulation in hematopoietic stem and progenitor cell regulation

The hemostatic system plays pivotal roles in injury repair, innate immunity, and adaptation to inflammatory challenges. We review the evidence that these vascular-protective mechanisms have nontraditional roles in hematopoietic stem cell (HSC) maintenance in their physiological bone marrow (BM) niches at steady-state and under stress. Expression of coagulation factors and the extrinsic coagulation initiator tissue factor by osteoblasts, tissue-resident macrophages, and megakaryocytes suggests that endosteal and vascular HSC niches are functionally regulated by extravascular coagulation. The anticoagulant endothelial protein C receptor (EPCR; Procr) is highly expressed by primitive BM HSCs and endothelial cells. EPCR is associated with its major ligand, activated protein C (aPC), in proximity to thrombomodulin-positive blood vessels, enforcing HSC integrin α4 adhesion and chemotherapy resistance in the context of CXCL12-CXCR4 niche retention signals. Protease-activated receptor 1-biased signaling by EPCR-aPC also maintains HSC retention, whereas thrombin signaling activates HSC motility and BM egress. Furthermore, HSC mobilization under stress is enhanced by the fibrinolytic and complement cascades that target HSCs and their BM niches. In addition, coagulation, fibrinolysis, and HSC-derived progeny, including megakaryocytes, synergize to reestablish functional perivascular HSC niches during BM stress. Therapeutic restoration of the anticoagulant pathway has preclinical efficacy in reversing BM failure following radiation injury, but questions remain about how antithrombotic therapy influences extravascular coagulation in HSC maintenance and hematopoiesis.