Journal of immunology最新文献

Human macrophages (MΦs) reside in tissues and develop tissue-specific identities. While studies in mice have identified molecular signatures for site-specific MΦ differentiation, less is known about the transcriptional profiles of human MΦs in distinct sites, including mucosal tissues and lymphoid organs during homeostasis and activation. Here, we use multimodal single-cell sequencing and ex vivo stimulation assays to define tissue signatures for populations of human MΦs isolated from lungs, small intestine, spleen, bone marrow, and lymph nodes obtained from individual organ donors. Our results reveal distinct tissue-adapted gene and protein profiles of metabolic, adhesion, and immune interaction pathways, which are specific to MΦs and not monocytes isolated from the same sites and exhibit homology to murine MΦs from the same sites. Tissue-adapted MΦs remained responsive to polarizing cytokine stimuli ex vivo, with upregulation of expected transcripts and secreted proteins, while retaining tissue-specific profiles. Patterns of chromatin accessibility in tissue MΦs identified from single-nucleus assay for transposase-accessible chromatin by sequencing reflected gene expression signatures and indicate that differential utilization of transcription factors may drive stable tissue-adapted profiles. Together, our findings show how human MΦ identity is coupled to their site of residence for mucosal and lymphoid organs and is intrinsically maintained during activation and polarization.

Pregnancy is characterized by dynamic immunological adaptations which are essential for maintaining both maternal and fetal health. The first-time use of coronavirus disease 2019 (COVID-19) vaccines in pregnant individuals presented an opportunity to discover pregnancy-specific immunoproteomic signatures across gestation. In this study, we profiled abundance levels of 1,451 unique proteins at baseline and in response to de novo COVID-19 vaccination in 466 samples from 278 pregnant individuals. Self-organizing map analysis identified 11 clusters of proteins based on similar longitudinal trajectories, with each cluster associated with distinct biological processes. Further functional characterization of protein expression levels across gestation revealed inflection points at 18-20 and 30-32 weeks of gestation, providing insight into expression dynamics of proteins associated with regulation of immune tolerance. Generalized additive modeling inferred gestational age-specific responses to the first and second dose of the vaccine; these highlight enrichment in proteins associated with cellular motility and canonical immune signaling after first and third trimester vaccination, but relative suppression of proteins associated with immune and inflammatory signal transduction pathways after second trimester vaccination consistent with diminished antibody responses when pregnant individuals are vaccinated exclusively in the second trimester. These findings advance our understanding of trimester-specific immune responses to vaccines, providing opportunities to enhance maternal and neonatal health.

Enhancing regulatory T cell (Treg) function offers a compelling therapeutic strategy for autoimmune disease. Engineered IL-2 muteins selectively expand functional Tregs with minimal impact on other immune cells, but their potential to compromise antiviral immunity remains largely unexplored. Here, we used a murine model of influenza A virus (Flu) infection to determine how IL-2 mutein shapes T cell responses to respiratory virus infection. IL-2 mutein administration prior to infection suppressed Flu-specific (Flu-sp) CD8 T cell responses and altered their localization and phenotype within the lungs, without affecting bystander CD8 T cells. This suppression correlated with reduced antigen presentation molecule expression on conventional dendritic cells (cDCs) early after infection but did not impact Flu-sp CD8 T cell priming. In contrast, administering IL-2 mutein during infection exacerbated disease and drove CD25-dependent expansion of Flu-sp CD8 T cells. Despite these opposing effects on effector responses, Fc.Mut24-treated mice generated robust antibody responses and protective T cell memory, which were maintained for at least 170 days. These findings reveal that Fc.Mut24 has temporally distinct effects on antiviral immunity, dampening early effector responses when given before infection, but enhancing effector expansion and disease severity when delivered during infection. Our results provide critical context for the therapeutic application of IL-2 muteins and highlight the importance of treatment timing in balancing immune modulation with protective immunity.

Regulatory T cell (Treg)-biased IL-2/anti-IL-2 monoclonal antibody complexes (IL-2c) can preferentially deliver IL-2 to CD25+ Tregs, causing proliferation of Tregs that is potentially advantageous in transplantation. We tested the ability of IL-2c to prolong murine cardiac allograft survival. C57BL/6 (H-2b) mice received fully major histocompatibility complex-mismatched BALB/c (H-2d) or hemi-allogeneic B6 × BALB/c (H-2b/d) F1 allografts. Recipients were treated prior to transplantation with IL-2c or control. Graft survival, anti-donor T cell priming, and donor-specific antibody production were measured. High-dimensional flow cytometry and transcriptomic analyses were used to characterize IL-2c-induced modulation of the alloimmune response. IL-2c treatment prolonged BALB/c allograft survival to 14 d (vs. 7 in control; P < 0.0001), and F1 allograft survival to 22 d (vs. 13 in control; P = 0.0018). Donor-specific T cell priming and antibody production were significantly reduced by IL-2c. Increased frequencies of CD4+CD25+FOXP3+ Tregs expressing high levels of ICOS, GITR, CD73, and CTLA-4 were identified in both the spleen and allograft in IL-2c-treated recipients. Reduced infiltration of F4/80+ cells into allografts and a marked reduction in intragraft myeloid activity were observed in IL-2c-treated recipients. When combined with a transient 21-d course of perioperative tacrolimus therapy, median survival time was extended to 48 d, and some recipients experienced indefinite allograft survival without ongoing immunosuppressive therapy. IL-2c increases Treg populations in priming and effector sites, is associated with downregulation of both the early adaptive immune response and myeloid response to cardiac allografts, and can synergize with tacrolimus to enable long-term graft survival.

Freshwater crayfish as most aquatic crustaceans live for up to 20-30 years on the bottom of lakes and rivers, constantly exposed to millions of microorganisms. Consequently, they must have an effective immune system to combat and eliminate pathogens. The main immune cells are the hemocytes, and they are regularly consumed during the animal's whole life and are continuously produced through hematopoiesis. We used DMSO as a tool to induce differentiation of hematopoietic stem cells and we can show that differentiation of hematopoietic stem cells to mature hemocytes in a freshwater crayfish is preceded by degradation of mitochondria by mitophagy and this process could be inhibited by a mitophagy inhibitor. The differentiation process was regulated by β-catenin signaling in similarity to differentiation of human neutrophils. A better understanding of the molecular mechanisms that regulate hemocyte development in these animals will provide new insights into the evolution of the innate immune system and hematopoiesis in general.

Candidozyma auris (formerly Candida auris) is an emerging multidrug-resistant pathogenic fungus that has rapidly spread across the world. Due to the high frequency of multidrug-resistant strains and mortality rate, C. auris is considered a critical health threat by the Centers for Disease Control and Prevention and the World Health Organization. Like other pathogens, C. auris employs virulence factors that are delivered by extracellular vesicles (EVs). We have shown that EVs from C. auris (CauEVs) activate murine phagocytes, boosting innate immune mechanisms. However, the effect of fungal EVs on lymphoid cells has not yet been addressed. Upon activation, CD4 T cells undergo clonal expansion and cytokine production that orchestrate immune responses to eradicate invading pathogens, a process of critical importance in controlling invasive candidiasis. Here, we show that the treatment with CauEVs inhibited the activation-induced CD4 T cells proliferation in a dose-dependent manner. Notably, we found that CauEVs acted at early events downstream to the T cell receptor signaling, inhibiting the MAPK phosphorylation. Interestingly, the inhibition of CD4 T cell proliferation by CauEVs was associated with an inhibition of the IL-2 signaling, followed by an increase on the IL-2 production that failed to restore proliferation. Taken together, our results suggest that CauEVs may contain an immunomodulatory factor(s) that affect the CD4 T cell activation and their fate from early to later events in a previously undescribed mechanism.

Neutrophils are the first line of defense against fungal infection and other microbial pathogens. Through alternative pathway of complement activation in innate immunity, complement fragments (opsonin) generated promote phagocytosis of the yeast forms of fungal pathogens such as Candida albicans. However, when complement levels are limited, through consumption in disease and inflammation or where microbial pathogens employ mechanisms to degrade or inhibit complement components, phagocytosis may still proceed via innate receptors, in the absence of effective opsonisation. Mechanisms of innate phagocytosis of fungi via neutrophils remain ill-defined and controversial. We have addressed this issue and demonstrated that neutrophils show very little phagocytosis of zymosan. Interestingly, activation or priming of neutrophils with phorbol-12-myristate-13-acetate, N-formyl-methionyl-leucyl-phenylalanine, arachidonic acid, tumor necrosis factor, and granulocyte macrophage-colony stimulating factor led to significant phagocytosis of the fungi. The result also demonstrated that priming led to a significant increase in the expression of the neutrophil Dectin-1, a receptor for β-glucan on zymosan. The increased phagocytosis induced by priming could be blocked with an anti-Dectin-1 antibody as well as the soluble β-glucan, laminarin, suggesting the importance of Dectin-1 in the phagocytosis of zymosan. The priming mechanism for phagocytosis and upregulation of Dectin-1 was examined using pharmacological inhibitors of protein kinase C (PKC) and p38 MAP kinase activation. The results showed that priming occurs in a PKC- p38-dependent as well as a PKC-independent p38-dependent manner. The findings demonstrate a highly regulated innate immune mechanism that potentially rapidly tackles microbial pathogens invading the bloodstream and tissues.

IgA-secreting plasma cells (PCs) provide durable humoral immunity by supplying critical antibodies to mucosal and systemic sites. These cells are found in large numbers in the gut lamina propria and the bone marrow (BM). In this study, we found that IgA+ PCs in the gut secrete significantly fewer antibodies on a per-cell basis compared to BM PCs in B6 mice. While the cell-intrinsic and -extrinsic signals responsible for regulating BM PC function have been extensively studied, these regulatory signals are understudied in gut PCs. Recent studies have established that metabolism is a critical component to optimized PC function in the BM. To evaluate the metabolic pathways utilized by tissue-resident IgA+ PCs, we utilized the flow cytometry-based SCENITH assay and determined that gut IgA+ PCs have increased glycolytic capacity, in contrast to increased mitochondrial dependency in BM IgA+ PCs. Consistent with a glycolytic phenotype, gut IgA+ PCs have a high capacity to uptake glucose, high mTORC1 activity, and low cellular reactive oxygen species. To determine if glycolysis is restricting gut IgA+ PCs' antibody secretion, we used inhibitors to target key bioenergetic pathways. We found that antibody secretion is enhanced by inhibiting the switch to glycolysis, and conversely restricted when PCs are prevented from utilizing oxidative phosphorylation. Herein, we identified that tissue-specific metabolic programs regulate PC function, where glycolysis restricts antibody secretion in the gut. Understanding how function is regulated in tissue-resident PCs can be leveraged to optimize better antibody responses for maintaining intestinal homeostasis, targeting mucosal pathogens, and optimizing mucosal vaccines.

Helper T cells (CD4 T cells) are lynchpins of adaptive immune responses. Each CD4 T cell expresses a single T-cell receptor, recognizing an epitope presented by major histocompatibility complex class II (MHC-II). Due to the enormous diversity of the T-cell repertoire, it is often desirable to study a population that responds to the same epitope. Here, we devised a novel method of selective immunization to produce a robust, monospecific helper T-cell response in mice using a modular mRNA vector. The vector encodes the target epitope attached via flexible linker to MHC-II. Immunization with this mRNA selectively elicits helper T-cell responses across a range of epitopes and MHC-II alleles. These CD4 T cells show robust, polyfunctional Th1 cytokine release when evaluated ex vivo. We tested the activity of these CD4 T cells in 2 disease models: Salmonella enterica and influenza virus. In both models, these monospecific CD4 T cells influenced the course of infection, demonstrating the utility of this experimental tool, which can produce a monospecific CD4 T-cell response.

Pinctada fucata martensii is an economically important mollusk in aquaculture, known for marine pearl production. The inflammatory response during the transplantation process was a key factor affecting pearl yield. Our previous studies have revealed the critical role of nicotinic acetylcholine receptors (nAChRs) from P. f. martensii in transplantation immunity. In this study, we obtained the 2,000 bp upstream sequence of the PmnAChR-6 gene and constructed promoter truncation plasmids, demonstrating that the core promoter activity region is located within the 1 to 500 bp upstream of the coding sequence. Organic cation transporter 1 (OCT-1) was predicted to be a key regulatory factor in the promoter region of PmnAChR-6. The dual luciferase assay results indicate that overexpression of OCT-1 reduces the promoter activity of the PmnAChR-6. Transcriptomic analysis of the pearl oyster after OCT-1 inhibitor (benzoylpaeoniflorin) treatment revealed that downregulation of PmOCT-1 led to significant enrichment of pathways such as apoptosis and endocytosis, along with elevated interleukin-17 levels in the serum. Furthermore, OCT-1 inhibitor treatment improved both the survival and nucleus retention rates of the transplanted pearl oysters. These findings indicate that PmOCT-1 participates in immune response by regulating expression of PmnAChR-6. The results of this study provide potential targets for effectively modulating immune responses during pearl production.