European Journal of Immunology最新文献

Staphylococcal enterotoxins (SE) crosslink the MHC-II on antigen-presenting cells (APC) with the T-cell receptor, inducing a polyclonal T-cell response. Although APCs are the initial targets of SE and are critical in shaping subsequent T-cell activation, the effects of SE on APC function remain poorly understood. This study investigates the immunomodulatory effects of staphylococcal enterotoxin A (SEA) on monocytes and their differentiation into monocyte-derived dendritic cells (moDC) or macrophages (MDM). Transcriptomic analyses of human monocytes via RNA sequencing revealed SEA-induced enrichment of gene pathways associated with inflammation, infection, and dermatitis, effects that were amplified in the presence of T cells. Phenotypic and functional characterization showed that SEA-primed monocytes differentiated into MDM with an altered polarization, deviating from classical M1/M2 pathways. SEA-primed MDM exhibited downregulation of key markers, including HLA-DR, CD80, CD86, and PD-L1. Functional assays demonstrated that SEA-primed MDM pushed hyperinflammatory T-cell responses, with significantly enhanced proliferation and IFN-γ secretion. In contrast, following SEA-priming, moDC retained robust antigen-presenting capabilities and displayed enhanced expression of molecules involved in T-cell interactions. These findings provide mechanistic insights into SEA-mediated immune modulation, illustrating how SEA reprograms MDM functions and amplifies proinflammatory T-cell responses. This advances our understanding of superantigen-driven immune interactions, offering a foundation for developing therapeutic strategies to mitigate superantigen-mediated immune conditions.

Immunoglobulin E (IgE)–mediated immediate hypersensitivity reactions underlie most allergic responses and are characterized by rapid mast cell (MC) activation and the subsequent release of mediators. These processes have been studied in rodent models via IgE or allergen sensitization, which replicate essential aspects of human allergic responses. Because allergic diseases exhibit diverse clinical manifestations, varying in phenotype, allergen specificity, immune response, and pathophysiological mechanisms, it is essential to employ a variety of models to comprehensively address distinct aspects of allergic responses and mechanisms. Allergic responses in mouse models can vary depending on factors such as experimental condition and murine strain, and these variations influence the ability of the model to reflect manifestations of human disease. This review aimed to summarize the characteristics of various murine allergy models, primarily focusing on wild-type strains, highlighting the impact of sensitization strategy, administration route, and murine strain on allergic disease outcomes. Given the pivotal role of MCs in allergic disease, achieving a deeper understanding of their characteristics across models is expected to enhance the applicability of these models and facilitate the development of MC-targeted therapies.

The efficacy of mRNA-based vaccines to prevent COVID-19 in autoimmune patients is controversial due to immunosuppressive therapies. Here, we characterized the T cell responses to SARS-CoV-2 in rheumatoid arthritis (RA) subjects, who received as few as one or up to seven vaccine injections. The study population had different disease severities and an association with other autoimmune comorbidities. All the subjects studied showed SARS-CoV-2 spike-specific CD4+ T helper (Th) cells in circulation, and in most of the subjects, CD8⁺ cytotoxic T cells. CD4⁺ and CD8⁺ T cells were CCR6+, suggesting trafficking to tissues. T cell memory did not correlate with the number of vaccine boosts received. Nonspike-specific T cells were enumerated in subjects who had symptomatic or asymptomatic COVID-19. Spike- and nonspike-specific regulatory T cells (Treg) were detectable in most subjects. CD4⁻ CD8⁻ double-negative (DN) T cells expanded in response to SARS-CoV-2 peptides. DN T cells co-cultured with autologous myeloid dendritic cells (DC) differentiated into CD8⁺ T cells, depending upon the strength of the stimuli. RA subjects responded to mRNA-based vaccination for COVID-19 protection, with no correlation with the number of injections. DN T cells differentiated into CD8⁺ T cells after stimulation, potentially exacerbating inflammation in RA vaccine recipients.

Effective antigen presentation by major histocompatibility complex (MHC) molecules to T cells is crucial for adaptive immunity. In type 2 diabetes mellitus (T2DM), metabolic dysregulation and chronic inflammation may impair these processes. We conducted a cross-sectional study to compare immune phenotypes between people with T2DM and healthy controls, and to correlate these findings with clinical parameters. People with T2DM exhibited augmented MHC I levels on B cells and CD14⁺ monocytes, and a shift in T cell polarization toward proinflammatory phenotypes. This was characterized by increased frequencies of type 1 cytotoxic T (Tc1) cells, and higher production of interferon-gamma (IFN-γ) and interleukin (IL)-10 by CD8⁺ T cells. Additionally, people with T2DM had higher frequencies of CD28⁺ and IFN-γ⁺ CD4⁺ T cells, and elevated expression of CD28, IFN-γ, IL-10, and IL-17A by CD4⁺ T cells. The shift toward a Tc1 phenotype correlated positively with blood glucose and negatively with insulin levels. Likewise, Th1 cell frequencies and IL-17 production by CD4⁺ T cells correlated positively with blood glucose, while IL-10⁺CD4⁺ T cell percentages correlated positively with insulin levels. Our findings suggest that T2DM is associated with a proinflammatory T-cell profile, polarization of which is linked to metabolic parameters.

Regulatory T cells (Tregs), defined by the lineage-specific transcription factor FoxP3, are crucial for immune regulation and have been studied extensively in mammals. However, avian Tregs remain poorly characterized, leaving gaps in our understanding of their evolutionary conservation and unique features. In this study, we investigated the phenotype of chicken Tregs to define reliable markers for their identification and characterization. We analyzed CD4⁺ splenocytes sorted into CD25^negative, CD25^low, and CD25^high subpopulations using RNA sequencing. FOXP3 and other Treg-associated genes were expressed in both CD25^low and CD25^high populations, showing that CD25 expression alone is insufficient to distinguish chicken Tregs. To refine the marker profile, we evaluated additional markers, including CTLA-4 and GITR. Notably, we describe for the first time a chicken-specific CTLA-4 antibody, which uniquely stains CTLA-4 exclusively in intracellular (ic) compartments, distinguishing it from mammalian counterparts. Single-cell RNA sequencing further confirmed distinct FOXP3⁺ clusters enriched for expression of CTLA4 and TNFRSF18 (encoding GITR). While CTLA-4's ic expression limits usability in functional assays, the combination of CD4⁺/CD25⁺/CTLA-4⁺/GITR⁺ represents the most accurate characterization of putative chicken Tregs to date. These findings highlight evolutionary conservation and species-specific differences in Treg markers, providing the foundation for future studies on chicken Treg functionality.

The widespread translation of cryptic proteins derived from the non-coding genome expands the complexity of the human proteome. A vast majority of cryptic proteins are expressed at low levels, rapidly degraded and efficiently presented on class I major histocompatibility complexes (MHC-I). On the other hand, some cryptic proteins are stable and functional and may integrate into the proteome through ongoing selective pressures. Herein, we propose a model in which the translation of cryptic proteins increases the diversity of functional proteins on which evolution can act and, during this trial-and-error process, provides a valuable source of antigens for immunosurveillance.

Severe COVID-19 is an immunological disorder characterized by excessive immune activation following infection with SARS-CoV-2, which typically occurs around the time of seroconversion. Anti-spike IgG of critically ill COVID-19 patients induces excessive inflammation by activation of Fc gamma receptors (FcγRs) on human alveolar macrophages, leading to tissue damage, pulmonary edema, and coagulopathy. While metabolic reprogramming of immune cells is critical for the induction of inflammatory responses, still little is known about the metabolic pathways that are involved in COVID-19-specific hyperinflammation. In this study, we identified that anti-spike IgG immune complexes (ICs) induce rapid metabolic reprogramming of alveolar macrophages, which is essential for the induction of inflammation. Through functional inhibition, we identified that glycolysis, fatty acid synthesis, and pentose phosphate pathway (PPP) activation are critical for anti-spike IgG-induced hyperinflammation. Remarkably, while excessive proinflammatory cytokine production by macrophages is critically dependent on simultaneous stimulation with viral stimuli and anti-spike IgG complexes, we show that the required metabolic reprogramming is specifically driven by anti-spike IgG complexes. These findings provide new insights into the metabolic pathways driving hyperinflammation by macrophages in the context of severe COVID-19. Targeting of these pathways may reveal new possibilities to counteract pathological inflammatory responses in severe COVID-19 and related diseases.

Mast cells are evolutionarily ancient immune cells located at strategic entry points for pathogens and allergens. Allergen exposure activates signal transduction pathways resembling those downstream of antigen receptors in T and B lymphocytes, leading to mast cell degranulation and cytokine secretion. The paralogous RNA-binding proteins ROQUIN-1 and ROQUIN-2 prevent aberrant T cell activation and differentiation and are cleaved upon antigen receptor engagement. Here, we investigated their roles in connective tissue mast cells using conditional gene knockout in mice. We show that ROQUIN-1 and ROQUIN-2 are dispensable for skin mast cell development and maintenance, while they are essential for serosal mast cells residing in the peritoneal and pleural cavities. Concurrent ablation of both paralogs did not affect mast cell degranulation in vitro and in vivo, nor did it alter activation-induced secretion of TNF and IL-6, cytokines that are regulated by ROQUIN proteins in other cell types. Furthermore, we globally define ROQUIN-regulated mRNAs in mast cells, and validate Runx1t1 and Ebi3 as indirect and Lfng as direct ROQUIN targets. Collectively, our results highlight the essential function of ROQUIN in connective tissue mast cells in serosal cavities.

This is an update to the Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition), Chapter 3: 12C, by Cossarizza et al. Administration of anti-ARTC2 nanobody(S+16a) prevents cell death during tissue processing. We demonstrate that the phenotype of CD44^midTreg is significantly impacted, whereas the eTreg phenotype remains stable following S+16a treatment, outlining specific protocols for population recovery.