Anti-DNA antibodies are a diverse set of antibodies that bind to structures on DNA that vary with clinical setting. In systemic lupus erythematosus (SLE), anti-DNA antibodies interact with the B-DNA backbone, binding DNA irrespective of species origin. In contrast, in the sera of otherwise healthy individuals (normal human subjects [NHSs]), anti-DNA antibodies bind to certain bacterial DNA. Furthermore, sera from patients with SLE and NHS controls can bind to the left-handed Z-DNA conformation. In the current studies, we have explored the antibody response to mycobacterial DNA from patients with tuberculosis (TB) and NHSs, focusing on DNA from Mycobacterium tuberculosis (Mtb) and Mycobacterium bovis bacillus Calmette-Guérin (BCG), given their high GC content and predicted capacity to form Z-DNA. Using ELISAs, we demonstrated that plasmas from patients with TB and NHSs contain antibodies to mycobacterial DNA, with a greater response to Mtb DNA than BCG DNA. To elucidate these findings, we conducted an in silico analysis with Z-Hunt-III, synteny analysis, and an in-house R Shiny program, Z-GENIE, to identify Z-DNA-forming sequences (ZFSs) and genomic regions that may be antigenic. Our analysis suggested that regions of difference and single-nucleotide polymorphism-generated ZFSs may contribute to sequence differences, which may influence antigenicity. Additionally, we provide evidence that shared sequences between DNA of Mtb and nontuberculous mycobacteria could explain the observed pattern of antibody reactivity. Together, these findings suggest that anti-DNA antibodies from patients with TB and NHS controls can distinguish between the DNA of different mycobacterial species and could serve as serological markers for infection or exposure.
Medical schools in the United States have varying curricular designs and limited instructional time, which challenge cohesive and comprehensive immunology coverage necessary for future physicians. To address this challenge, the American Association of Immunologists formed a Medical Education Immunology Curriculum Task Force, to generate recommendations for U.S. medical schools in the field of immunology. In June 2024, faculty from all U.S. medical schools were invited to participate in an initial research survey designed to assess the current field of immunology content taught to medical students. Approximately 30% of the invited participants responded, with 25% of respondents from DO programs and 75% from MD programs, which reflects the overall distribution of these schools nationally. This article shares the core content identified by the participating faculty, along with various demographic and opinion-based metrics. The Task Force developed specific learning objectives (LOs) and associated immune-relevant clinical conditions for each core area of content. These were then vetted by the broader medical immunology education community by presentation at an immunology-focused professional meeting and through a second feedback survey. The final recommended content includes foundational topics and associated LOs, as well as a list of key associated clinical conditions aligned with each foundational topic. These LOs have the advantage of being inserted throughout integrated curriculum and/or could be used in stand-alone immunology course blocks in the medical school curriculum. The inclusion of these LOs in a medical curriculum will sufficiently educate future physicians regarding the impact of the immune system on overall health and illness.
TNF receptor-associated factor 1 (TRAF1) is a prosurvival signaling adaptor that contributes to NF-κB activation downstream of a subset of TNF receptor superfamily members. TRAF1 is overexpressed in many cancers of mature B cells, including chronic lymphocytic leukemia (CLL). Previous studies have established that TRAF1 S146 is a target of phosphorylation by the kinase PKN1 and that PKN1 is required to prevent cellular inhibitor of apoptosis protein (cIAP)-dependent degradation of TRAF1 in the CD40 signaling complex. The kinase inhibitor OTSSP167 inhibits PKN1 in the nanomolar range and its addition to primary CLL cells was previously shown to induce dose-dependent loss of TRAF1 and concomitant increases in activated caspase 3 and cell death. These studies identified PKN1 as a target for therapy of CLL. To identify more potent and specific PKN1 inhibitors for therapy of B-cell cancers, it is important to measure a direct target of PKN1, such as phospho-TRAF1. To this end, here we use overexpression of an S146A mutant of human TRAF1 in HEK293 cells to validate a recently generated TRAF1 phospho (p)S146-specific antibody and to confirm that this phosphorylation is lost upon treatment with OTSSP167. Using CRISPR/Cas9 knockout in RAJI cells, we also show that both PKN1 and the closely related family member PKN2 can phosphorylate TRAF1 S146. We further show that TRAF1 S146 is constitutively phosphorylated in OP9 cultured primary human CLL cells, including those with p53 mutations, and that this phosphorylation is sensitive to inhibition with OTSSP167. These findings provide support the development of more potent PKN1/2 inhibitors for CLL.
Progesterone exerts important immunomodulatory functions, yet the immune effects of structurally diverse synthetic progestins remain incompletely defined. Given their variable receptor-binding profiles and links to altered inflammatory outcomes, we examined how commonly used progestins regulate immune signaling in primary human cells. Peripheral blood mononuclear cells from healthy female donors were exposed to physiologically relevant concentrations of natural progesterone (P4) and representative synthetic progestins spanning multiple generations. Cytokine responses were quantified at both the protein and transcript levels. Baseline steroid receptor expression and age of donor was correlated with cytokine output. High-dimensional flow cytometry coupled with unsupervised clustering was used to define the cellular sources of inflammatory cytokine production. In parallel, naïve CD4+ T-cell differentiation was performed to determine effects on T helper (Th) cell polarization. Only P4 induced immunoregulatory cytokine IL-10, whereas all progestins, except first-generation norethindrone, induced markedly higher IL-6 production compared with media control. Gene expression analysis confirmed induction of multiple proinflammatory genes at physiologically relevant concentrations. High-dimensional flow cytometry identified CD14+ monocytes as the dominant cellular source of IL-6 following progestin exposure. In contrast, P4 selectively suppressed Th1 differentiation and promoted Th2 lineage commitment, whereas synthetic progestins failed to reproduce these immunoregulatory effects. Together, these findings demonstrate that synthetic progestins differentially regulate innate and adaptive immune responses compared with P4 and promote proinflammatory responses that may influence immune homeostasis.
Active learning and flipped classrooms have gained popularity in higher education due to their ability to improve educational outcomes. This study evaluated whether combining voiceover lectures and review games could improve learner engagement and satisfaction while achieving learning outcomes comparable to those of traditional immunology didactic lectures. A total of 123 first- and second-year medical students were randomly assigned to groups that took formative quizzes on immunology material after exposure to either: (i) a traditional didactic lecture, (ii) a voiceover lecture followed by an in-class discussion of the voiceover and subsequent review game, or (iii) a blind control group that had no exposure to the material. Furthermore, students provided feedback on the pedagogy and their learning preferences. Students were very enthusiastic about the review games and preferred shorter voiceovers containing formative questions embedded within the voiceover. Importantly, there was no significant difference in quiz performance between the 2 pedagogies, and both groups performed significantly better than the blind control group. A slight but significant decrease in student preference for voiceovers was noted throughout the duration of this multiyear study, which occurred during and shortly after the COVID-19 pandemic. Faculty who observed this pedagogy expressed an increased willingness to use voiceovers and review games if they received training and information technology support. Collectively, this longitudinal study demonstrated support from both faculty and students for the combined use of voiceovers plus review games and captured a potential shift in medical student preferences for learning in recent years during the COVID-19 pandemic.
The immune system is always acting to protect the body from the microbial world, especially at the openings of the body but also helps to maintain homeostasis. Normal functions include self-regulation and regeneration, facilitating the maintenance of organs, skin and mucosal membranes, protecting the openings of the body, providing surveillance for abnormal and cancer cells and eliminating molecular and cellular debris. In addition to status quo maintenance functions, the immune system responds to damage, disruption or danger when challenged by trauma, infection, cancer, autoimmunity and other diseases. The responses are communicated and coordinated to other cells, tissues, organs, and systems through cell-cell interactions, with different soluble molecules including cytokines. Cytokines are the language of the immune system and define the progression of the subsequent immune response. Each cytokine may elicit its own responses but by acting together in a conversation they communicate and coordinate the intended actions to maintain the status quo or respond to challenge. These conversations include regulation/tolerance, alarmins, acute phase cytokines, Th1, Th2, Th17, and Th22. The cytokine conversations, their conversationalists (the cells eliciting and responding to cytokines), and the basic responses of the immune system will be discussed. An easy way to remember the conversations is provided.
Regulatory CD4+ T cells (Tregs), as defined by expression of the transcription factor Foxp3, strongly depend on the cytokine interleukin 2 (IL-2) for their survival and function and are often identified by the combination of high IL-2Rα (CD25) and low IL-7Rα (CD127) expression. Nevertheless, subsets expressing higher levels of IL-7Rα have been described, and IL-7 signaling does play a role in Treg function in some specific biologic contexts and tissues. The precise role of IL-7Rα-expressing Tregs in autoimmunity remains poorly defined though, potentially hampering current efforts to develop IL-7Rα blockade for the treatment of various autoimmune diseases. To ask whether cell-intrinsic IL-7Rα expression in Tregs was required for their function during type 1 diabetes (T1D) development, we generated non-obese diabetic (NOD) mice in which IL-7Rα is exclusively deleted in Foxp3-expressing Tregs. In young NOD mice, IL-7Rα deficiency did not alter Treg numbers and phenotype. However, 100% of NOD mice with IL-7Rα-deficient Tregs became diabetic, while the T1D incidence is typically around 50-60% in our colony. This increased susceptibility for T1D indicates that IL-7Rα expression in Tregs is required to protect a subset of NOD mice against islet autoimmunity. At the time of T1D onset, CD4+ and CD8+ T cells from NOD mice with IL-7Rα-deficient Tregs showed increased IFN-γ and IL-2 cytokine production. Our data demonstrate that cell-intrinsic IL-7R signaling in Foxp3+ Tregs is required to suppress effector T cell responses and to prevent full penetrance of T1D in NOD mice.
A key aspect of cystic fibrosis pathophysiology is the significant role played by neutrophils, central to the inflammatory response in cystic fibrosis airways. Neutrophil-dominated inflammation greatly influences clinical outcomes, including airway damage and lung function decline. People with cystic fibrosis have an increase in circulating neutrophils that exhibit numerous functional and phenotypic abnormalities. We used spectral flow cytometry to delineate the expression of 24 cell surface markers on neutrophils from 24 healthy donors and 45 adults with cystic fibrosis, before and after elexacaftor-tezacaftor-ivacaftor treatment. This comprehensive analysis examined phenotypic markers associated with fundamental neutrophil functions, including differentiation, maturity, activation, antimicrobial activities (degranulation, pathogen sensing and chemotaxis), metabolism, and immunomodulation. Prior to treatment, neutrophils from adults with cystic fibrosis displayed a phenotype suggestive of immune activation and metabolic aberration. Treatment with elexacaftor-tezacaftor-ivacaftor normalized a FPR1high/CXCR2high subset, an observation consistent with enhanced pathogen-sensing capacity. The treatment, however, failed to restore fully normal phenotypes in cystic fibrosis neutrophils but rather induced the modulation of a PD-L1high/CD114high/GLUT-1high subset of mature neutrophils with an increased expression of PD-L1 and adhesion molecules such as CD11c and CD11b. Taken together, our data reveal a specific immunophenotypic signature of neutrophils in cystic fibrosis that is further modified by treatment with elexacaftor-tezacaftor-ivacaftor, suggesting the opportunity for developing adjunctive therapies to enhance beneficial antimicrobial subsets while simultaneously mitigating immunosuppressive phenotypes, thereby opening new perspectives for immune modulation in cystic fibrosis treatment.
Obesity is increasingly recognized as a state of chronic low-grade inflammation associated with altered immune cell function, yet the mechanisms driving these changes remain incompletely understood. This study investigated myeloid cell subpopulations and neutrophil behavior in adult participants exhibiting preclinical obesity (body mass index [BMI] 32-51 kg/m2, n = 12) compared to normal-weight controls (BMI 21-24 kg/m2, n = 9), correlating findings with metabolic and inflammatory markers. Peripheral blood samples were analyzed by flow cytometry to quantify myeloid cell populations and TLR4/IL-1R surface expression. Neutrophils were cultured under normoxic (18% O2) or hypoxic (1% O2) conditions, with or without glutaminase inhibition, to assess spontaneous neutrophil death. Participants with preclinical obesity exhibited increased monocyte numbers and eosinophils, whereas total neutrophil numbers were not significantly different between groups, together with a higher percentage of HLA-DR-/low monocytes and activated immature (CD16-CD11b+CD10-) neutrophils. In participants under 60 yr of age, IL‑1R expression on monocytes was significantly increased in the obesity group. Significant metabolic differences were also noted, including higher A1c (5.9 ± 0.1% vs 5.3 ± 0.1%), hs-CRP (9.01 ± 3.33 vs 0.69 ± 0.17 mg/L), and alkaline phosphatase (102.33 ± 9.67 vs 65.75 ± 5.54 U/L) in the preclinical obesity cohort, alongside decreased mean cell hemoglobin. Ex vivo neutrophil culture revealed that hypoxia reduced spontaneous neutrophil death in both groups; however, this effect was significantly reduced by glutaminase inhibition specifically in neutrophils from participants with preclinical obesity, suggesting a heightened reliance on glutamine metabolism for survival under hypoxia. These findings demonstrate dysregulated myelopoiesis and altered neutrophil behavior in preclinical obesity, providing mechanistic insight into the early immune consequences of metabolic dysfunction.
The use of animals in education and research has received increased scrutiny due to ethical and pedagogical considerations. Researchers have used non-animal models in immunology, medical, and veterinary disciplines for decades. Conversely, in education, there has been a reduced focus on teaching the theoretical and practical applications of these technologies. This has resulted in a gap between research and practice, limiting student exposure to the potential advantages of these technologies. In the last few decades, as non-animal technologies have become more sophisticated and widely available, the traditional reliance on animal models has slowly declined. With the emergence of new approach methodologies (NAMs), including organoids, organ-on-chip systems, bioprinting, computer simulations and other interactive digital tools, these offer authentic experiences while significantly reducing the need for animal use. Technologies such as organoids and computer simulations are now being increasingly introduced into undergraduate education. This "On The Horizons" narrative examines current non-animal model technologies, their benefits and limitations, and their implications for the evolving landscape of higher education. Importantly, the technologies covered in this paper have the potential to improve the student experience in programs that traditionally require the use of animals.
Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterized by dysregulated B cell responses and pathogenic autoantibody production. Given the central role that B cells play in SLE pathogenesis, we aimed to characterize genetic variation within the B cell compartment of African ancestry (AFR) women with SLE who are disproportionately and more severely affected by SLE. Here, we analyzed RNA-seq data from a previously published study of high disease activity AFR SLE individuals and healthy controls (HC) to identify coding variants in B cells with potential functional consequence that may underpin disease. In this cohort, we identified 575 missense variants associated with 158 unique genes. While many variant-containing genes did not exhibit large transcriptional changes between cohorts, a subset occurred within genes involved in B cell signaling, activation, and differentiation. However, genes enriched in AFR SLE were consistently upregulated across multiple B cell subtypes, suggesting that variant-associated transcriptional changes occur broadly across the B cell compartment and not within a single subset. Among these, the TNFAIP3 variant rs2230926 was enriched in AFR SLE individuals and occurs at a substantially higher allele frequency in AFR populations. This study provides insights into genetic variation found within the B cell compartment that may contribute to immune dysregulation and disease pathogenesis in SLE in AFR populations.
Sepsis is a life-threatening systemic inflammation marked by an initial hyperinflammatory phase. Tregs are pivotal in tempering this early immune response. Semaphorins, originally neuronal guidance cues, have emerged as immune modulators. Notably, Sema3E influences dendritic cell and T cell responses, but its role in Treg-mediated regulation during endotoxemia is unclear. WT and Sema3e-/- mice were subjected to LPS-induced endotoxemia. Treg frequencies, proliferation and migration were assessed by flow cytometry and Transwell assays, respectively. Serum cytokines (eg IL-10) were quantified using ELISA. A TNFRSF25 agonist was administered to expand Tregs in vivo, and adoptive transfers of WT or Sema3e-/- Tregs were performed. Clinical scores and survival were recorded. Sema3e-/- mice exhibited significantly impaired Treg expansion and proliferation, altered migratory patterns with reduced Treg accumulation in spleen and lymph nodes, and consequently lower serum cytokine levels (eg IFN-γ) compared to WT, correlating with exacerbated disease severity. DR3-mediated Treg expansion in Sema3e-/- mice did not improve their clinical outcomes. Furthermore, adoptively transferred Sema3e-/- Tregs failed to confer protection in endotoxemic recipients, unlike WT Tregs. Sema3E is essential for optimal Treg responses and immune regulation during severe LPS-induced inflammation. Its absence compromises Treg expansion, localization, and function, worsening sepsis outcomes. These findings highlight Sema3E as a critical component of Treg-mediated immunosuppression and a potential therapeutic target for improving immune homeostasis in sepsis.
Natural antibodies (NAbs), primarily produced by CD5+ B-1 cells, provide critical early protection against infections such as Streptococcus pneumoniae. The structure of these natural antibodies, germline-like with minimal N-additions, is essential for their protective capacity. The protective capacity and germline status of NAbs are compromised in aged male mice but maintained in aged female mice. CD5+ B-1 cells are maintained through self-renewal, necessary for maintaining germline-like natural antibodies, and this process depends on autophagy. Intermittent fasting enhances autophagy and stem cell self-renewal, suggesting that it may influence B-1 cell persistence and natural antibody structure. Young (4-wk-old) male and female mice were placed on a fasting regimen (24-h fast weekly) or fed ad libitum for 12 wk. Here, we show that intermittent fasting modulates the antigen-specific natural IgM repertoire of young male and female mice, altering both peritoneal and splenic phosphatidylcholine-specific CD5+ B-1 cell repertoires, with the most pronounced effects in the spleen. Intermittent fasting increased the prevalence of germline-like (few N-additions) antibodies and led to an increase in VH11 usage, a variable gene mainly utilized during fetal development. Fasting also affected components of the serum repertoire; however, these effects differed between male and female mice. Female mice showed a significant decrease in phosphorylcholine- and pneumococcal polysaccharide serotype 3-specific IgM levels, whereas male mice showed a significant increase in phosphatidylcholine-specific IgM levels. We also observed a significant decrease in splenic CD5+ B-1 cells and serum interleukin-5 levels after fasting. These results suggest that intermittent fasting may help preserve or restore protective NAbs.
Patients with myelodysplastic syndrome (MDS) are immunocompromised and are therefore susceptible to fatal infection. While neutropenia and neutrophil dysfunction account for much of this immunodeficiency, other immune cells likely also contribute. In contrast to the extensive study of neutrophils in MDS, there has been very little investigation of macrophage host defense function in MDS. In the current study, we find that macrophage differentiation and macrophage phagocytosis of bacteria are greatly weakened in patients with MDS, regardless of patient genotype. Moreover, we find that killing of those bacteria that are ingested is diminished in MDS patients with high-risk disease. Using a mouse model that expresses the MDS-associated U2AF1-S34F mutation, we find that this mutation is sufficient to induce macrophage functional defects. We conclude that macrophage host defense defects likely contribute to the immunodeficiency present in MDS.
Signal regulatory protein gamma (SIRPγ) is a T cell-specific surface receptor in the human immune system with previously undefined function in human CD8 T cell differentiation. We report that SIRPγ expression varies substantially across individuals and stratifies CD8 T cell differentiation states. Individuals with low SIRPγ expression exhibit an increased frequency of CD27-CD45RO+ effector-like and CD27-CD45RO- terminally differentiated CD8 T cells, while high expressors retain a predominance of naïve and central memory cells. To investigate the functional role of SIRPγ, we performed small interfering RNA-mediated knockdown in naïve human CD8 T cells. Under suboptimal TCR stimulation, SIRPG knockdown drove robust effector-like differentiation marked by increased CD45RO expression, T-bet upregulation, and enhanced production of TNF-α, IFN-γ, and granzyme B. This phenotype was not recapitulated by CD47 blockade, indicating that SIRPγ modulates differentiation through a CD47-independent mechanism. These findings identify SIRPγ as a negative regulator of CD8 T cell effector programming under limiting stimulatory conditions. Interindividual variability in SIRPγ expression may influence immune homeostasis and susceptibility to immunopathology, highlighting SIRPγ as a potential therapeutic target in settings of dysregulated T cell responses.
Systemic lupus erythematosus (SLE) is a progressive antibody-mediated autoimmune disease characterized by systemic immune complex deposition. A subset of SLE patients has elevated CD4+IL-9+ T cells as well as increased levels of secreted interleukin (IL)-9 and IL9 messenger RNA compared with healthy control subjects. However, because IL-9 can have both pro- and anti-inflammatory effects in autoimmune disease, its function in SLE is unclear. We use the MRL/lpr murine model of SLE to demonstrate that IL-9 exhibits protective activity in the early stages of disease. Treatment of these mice with an IL-9 neutralizing antibody from 6 to 12 wk of age results in an expansion of immune cells, leading to exacerbation of disease. In contrast, treatment with anti-IL-9 from 6 to 18 wk of age does not significantly alter disease course compared with isotype control. Anti-IL-9 antibody treatment of these mice results in reduced systemic IL-2 levels, IL-9+ type 2 innate lymphoid cells, and regulatory T cells in the kidney, suggesting an IL-9-dependent suppressive cellular circuit similar to that observed in rheumatoid arthritis. Importantly, supplementation of IL-2 during IL-9 blockade recovers regulatory T cell numbers and limits disease. Together, these data demonstrate an IL-9-dependent suppressive circuit that is evident early in the development of SLE which may be amenable to manipulation to achieve a therapeutic benefit.
Mast cells are critical players in the maladaptive immune responses underlying biphasic reactions in allergic inflammation. Neurogranin (Ng) is an IQ domain-containing protein that sequesters Calmodulin under low [Ca2+] and negatively regulates calmodulin-mediated signaling such as calcineurin activation, in addition to downstream inflammatory responses. Previously described as brain specific, Ng has recently been identified in the spleen, bone marrow, and B lymphocytes, highlighting the need to investigate its negative regulatory role in other proinflammatory contexts. Here, we sought to determine the role of Ng in allergen-activated mast cells, to better understand the negative regulatory mechanisms that can potentially be exploited to help alleviate the severity of allergic inflammation. Using bone marrow-derived mast cells from wild-type (Nrgn+/+) and heterozygous (Nrgn+/-) mice, we identified that Ng is present in mast cells. It was determined that although Ng did not influence the development of mature mast cells or the extent of early-phase inflammation, a reduction in Ng significantly increased gene expression of IL6 and IL13, which was coupled with an increase in release of IL-6, IL-13, TNF, CCL1, CCL2, and CCL3. Together, this is the first study to identify Ng in mast cells, in addition to positioning its role as a negative regulator of mast cell responses following allergen activation. These data highlight the need for future research to further elucidate the role of Ng in IgE-mediated mast cell activation to better understand the regulatory mechanisms of these inflammatory cells in mast cell-driven normal and pathological contexts.
The effect of exercise on immune system activation and regulation has been well studied in athletes following long-duration exercise and elite events, and across various modalities; however, little work has been performed using shorter-duration, high-intensity protocols and in recreational athletes. This study examined the comparative effects of both treadmill running and stationary cycling, high-intensity interval training (HIIT) on circulating inflammatory biomarkers. A total of 26 young, healthy participants completed both exercise modality protocols in a randomized order using a crossover design. Blood samples were collected at baseline, immediately after exercise, and 1 and 24 h postexercise time points, then processed for cytokine concentrations. Interleukin (IL)-6 increased immediately following both exercise modalities (P < 0.001). IL-8 increased following treadmill running (P = 0.02) and continued to increase during 1 h and 24 h recovery postexercise (P < 0.001). IL-10 increased following 24 h recovery in treadmill running (P < 0.01) and stationary cycling (P < 0.05). There were no significant changes in IL-1ra or tumor necrosis factor α. C-reactive protein trended to increase 24 h after treadmill running with a large effect size (η2 = 0.22). Treadmill running and stationary cycling HIIT provide the necessary stimulus to alter circulating cytokine concentrations. IL-6 and IL-10 increased to the same extent following both exercise modalities. IL-8 was found to increase significantly following treadmill HIIT but not following cycling HIIT. These findings may inform the design of future studies investigating the influence of HIIT on measures of inflammation and health in healthy and clinical populations.
Monocyte-macrophage lineage cells, crucial components of the innate immune system, can uniquely form bone-resorbing osteoclasts upon exposure to the cytokine receptor activator of nuclear factor κB ligand (RANKL) in the bone microenvironment. Recent studies have also begun to uncover extensive extraskeletal roles of RANKL. However, how monocyte-macrophage lineage cells respond to RANKL outside of the bone, and the impact that this signaling pathway exerts on the host immune response, is not fully understood. In this study, we sought to define how RANKL exposure shapes the macrophage inflammatory response to pathogens by using the model intracellular bacterium Salmonella enterica serovar Typhimurium, which coopts macrophages to cause life-threatening infections. We found that exposing both mouse and human macrophages to subosteoclastogenic levels of RANKL increased intracellular Salmonella enterica serovar Typhimurium burdens and decreased proinflammatory cytokine production. RNA sequencing revealed downregulation of pattern recognition receptor signaling pathways in RANKL-treated macrophages during the early stages of infection. Therefore, we hypothesized that RANKL impairs pattern recognition receptor-dependent signaling pathways that are important for proinflammatory cytokine production. We discovered that RANKL-treated macrophages exhibit reduced nuclear factor κB and interferon regulatory factor 3 activation, specifically in response to Toll-like receptor 2 (TLR2) and TLR4 stimulation. We determined that prior RANKL exposure decreases abundance of the TLR2 and TLR4 adaptor proteins TRAM (TRIF-related adaptor molecule) and TIRAP (TIR domain-containing adaptor protein). Together, these data suggest that RANKL exposure negatively impacts the macrophage TLR-mediated inflammatory response to bacteria.
Malaria, caused by Plasmodium species, is one of the most widespread illnesses globally, affecting millions of individuals each year. The complex life cycle of these parasites requires a multifaceted approach from the human immune system to respond to infection. Additionally, Plasmodium parasites have coevolved in primates and developed numerous immune evasion mechanisms to escape human immune defenses. Here, we provide an up-to-date review of the human immune responses to blood-stage malaria, as well as the parasite immune evasion mechanisms during this part of the life cycle.
