Discovery immunology最新文献

[This corrects the article DOI: 10.1093/discim/kyaf008.].

Introduction: Understanding factors that shape immune responses in wild animals is critical to predicting population resilience and long-term persistence. Immune function modifies the survival of individuals facing infectious disease, trauma, and environmental stressors, yet remains understudied. An individual's immune response is shaped not only by current and historic pathogen exposures but is mediated by both individual (e.g. host genetics, metabolic plane, age, and sex) and population-level (e.g. population size, density, and connectivity) factors. Bighorn sheep (Ovis canadensis, bighorn) occupy populations of varying sizes, nested within larger metapopulations, creating a hierarchical structure. This organization provides a useful framework to understand how immune parameters vary across individual, population, and metapopulation levels. Unfortunately, measurement of immune parameters in ungulates is limited.

Methods: To address this limitation, we measured 18 immunologic traits across 581 wild bighorn to evaluate this toolkit's ability to detect immunological differences between individuals, populations, and metapopulations.

Results: Most immunological phenotypes illustrated significant variation at the metapopulation level and individual level. Our assays revealed immune phenotypic variation consistent with two main axes of segregation-one that distinguished tradeoffs in bighorn innate versus adaptive immune responses, and another reflecting alternative inflammatory states, defined by distinct cytokine patterns. Bighorn age and sex also mediated immune response patterns.

Conclusions: Our immunological toolkit sets the stage to further clarify landscape-level immunological variation in wild ungulate populations and provides a template for deploying integrative eco-immunological tools in any natural population to further understand wildlife health.

Introduction: Monoclonal antibodies (mAbs) are critical tools for elucidating viral evolution, informing vaccine design, and developing antiviral therapeutics. Large-animal models, such as the pig, that closely mirror human immune responses are essential for understanding influenza immunity.

Methods: Pigs were either infected or sequentially immunized with influenza viruses and monoclonal antibodies directed against H3, H5, and H7 influenza virus haemagglutinins were isolated. Antibody specificity, breadth, epitope targeting (head versus stem), neutralizing capacity, and Fc-mediated activity were assessed across influenza subtypes.

Results: Pigs generated both strain-specific and broadly reactive mAbs targeting haemagglutinin head and stem epitopes. An H3-specific mAb (H3-57) selectively recognized the egg-adapted L194P mutation associated with reduced human vaccine effectiveness. H5 and H7 immunization induced neutralizing antibodies, including cross-group stem mAbs reactive with H1, H3, and H5 haemagglutinins. Fc-mediated activity correlated with antibody binding strength rather than epitope location.

Conclusions: These findings demonstrate that pigs mount antibody responses closely resembling those observed in humans, including recognition of conserved stem epitopes and adaptive head mutations. Porcine mAbs represent powerful new tools for dissecting influenza immunity, guiding vaccine design, and enhancing pandemic preparedness using a physiologically relevant large-animal model.

Introduction: The intestinal roundworm Heligmosomoides bakeri establishes chronic infections in susceptible C57Bl/6 mice, yet repeated ('trickle') infections confer immunity and promote worm clearance. We previously linked this acquired immunity to enhanced intestinal granuloma formation. Here, we focused on effector molecules (antibodies) and cells (eosinophils and macrophages) known to immobilize and damage developing parasites.

Methods and results: We used flow cytometry and immunofluorescence to show that granulomas in trickle-infected female mice contain elevated levels of IgG₁, SiglecF⁺ eosinophils and CD206⁺ macrophages compared to bolus-infected animals, while IgG2c, IgA, and IgE were undetectable and levels of Ly6G⁺ neutrophils or NK1.1⁺ NK cells were unchanged. To mimic natural complexity, we introduced a mixed immune environment via prior Toxoplasma gondii infection which induces interferon-γ production in the small intestine. Co-infected mice exhibited fewer and smaller granulomas, which lacked IgG₁, SiglecF⁺ eosinophils, and CD206⁺ macrophages, correlating with higher worm burdens.

Conclusion: Together, these findings highlight the importance of local immune responses to tissue-invading worms and help explain why helminth elimination is frequently more difficult in the complex immune environments found in field settings compared with laboratory conditions.

Introduction: Trichuris trichiura (whipworm) is a gastrointestinal nematode that infects approximately 465 million people worldwide. Trichuris muris is used as a tractable model for the human whipworm. In wild-type mice, infection with a high dose of T. muris eggs leads to worm expulsion, which is dependent on a CD4Th2 response and interleukin (IL-)13 production. T cells up-regulate glycolysis and uptake of substrates following activation. The amino acid transporter SLC7A5 has been shown to be necessary for activation of mTORC1, a nutrient/energy/redox sensor critical for T cell differentiation into effector cells.

Methods and results: We found that mice lacking SLC7A5 in CD4T cells have significantly delayed worm expulsion, associated with reduced IL-13, reduced pmTOR, and reduced glycolytic rates. However, as infection progressed, IL-13 levels recovered in T cell-specific SLC7A5-deficient mice, alongside resistance. The critical role of CD4T cell metabolism per se and downstream mTOR in CD4T cells in host resistance was shown in mice lacking mTOR in CD4T cells that failed to expel their parasites and developed chronic infection.

Conclusion: Our study shows that mTOR is essential for optimal functioning of T cells during whipworm infection and that deletion of Slc7a5 significantly delays worm clearance indicating a key role for amino acid acquisition by CD4T cells in resistance to helminth infection.

Introduction: Wild animals live in a pathogen-rich environment and are normally infected with a wide range of micro- and macro-parasites. Wild animals' T cells are central to the effectiveness of their adaptive immune response in ameliorating the effect of these infections. Here, we have investigated the T-cell receptor (TCR) repertoire of wild mice to investigate how it varies in animals of different ages and sex and from different sites.

Methods: We sequenced the TCR alpha and beta chains of CD4⁺ and CD8⁺ T cells of 65 wild Mus musculus domesticus from two UK sites.

Results: We analysed repertoire richness and diversity finding that wild mice have large TCR repertoires. Repertoire richness, which measures the breadth of the repertoire, was not significantly affected by mouse age or sex, suggesting that wild mice maintain the capacity to respond to novel antigens throughout their lives. In contrast, repertoire diversity (measured by Shannon's index) was affected by a mouse sex-by-age interaction. This low diversity, coupled with constant richness, points to older mice having comparatively more highly abundant clones in their repertoires, perhaps due to chronic exposure to persistent pathogens in their environment.

Discussion: These findings provide a novel description of the wild mouse TCR, revealing an immune system that balances maintaining a broad response capacity with developing strong, lasting responses to infections in the natural environment.

The induction of immune tolerance, a state of immunologic hyporesponsiveness to an antigen, is essential to prevent the destructive potential of the immune system in response to harmless or beneficial agents. Early efforts to understand tolerance focused on model stimuli, self-antigens, transplanted organs, and the growing fetus. Through co-evolution, the microbiome and the host immune system have developed strategies that promote immunological tolerance to the microbiome. This dialogue ensures the maintenance of mutualistic interactions that provide a stable habitat for the microbiome which in turn confers numerous physiological benefits to the host. Despite the gut microbiome being a potent inducer of immune tolerance, the mechanisms through which specific members shaped immune function remained largely ignored for decades. The growing appreciation for the immunomodulatory capacity of the microbiome has led to a massive expansion of efforts to define how the balance between tolerance and inflammation is induced and maintained at mucosal sites like the intestine. While the ensuing research uncovered myriad fundamental insights into the concerted host and microbial functions promoting host-microbiome mutualism, inducing tolerance to clinically relevant antigens remains a major challenge in the development of tolerogenic therapies. Here, we trace the interaction between intestinal CD4+ T cells and the microbiome, from antigen uptake through to the development of a polarized collection of CD4+ T cells, whose functions are essential for immunological tolerance, and highlight the knowledge gaps that limit efforts to leverage these interactions for clinical benefit.

Introduction: CASPASE8 promotes both cell death and survival by acting as a trigger of apoptosis and a repressor of necroptosis. In T cells, the function and mechanisms of CASPASE8 are incompletely understood.

Methods: Here, we analysed mice in which Casp8 was conditionally deleted in T cells at different stages of development.

Results: In mice with deletion early in T cell development, we observed a modest reduction in early thymic progenitors and a striking absence of NKT cells in the thymus. Amongst mature peripheral T cells, there was a substantial and specific reduction in the CD8 T cell compartment, which included naive, central memory and virtual memory subsets. Using a tamoxifen-inducible CD8^CreERT to delete Casp8 revealed an acute requirement for continued CASPASE8 expression for survival of a fraction of mature CD8 T cells. Analysing Casp8-deficient mice that express a kinase dead RIPK1 suggested that in vivo, necroptosis contributed to death of thymic progenitors and CD8EM and CD8CM subsets. However, kinase dead RIPK1 failed to restore NKT cell development or rescue the loss of CD4EM and CD4CM in mixed bone marrow chimeras, and only partially rescued CD8 VM T cell.

Conclusions: Together, these observations suggest that CASPASE8 promotes T cell survival independent of its established role in repressing RIPK1-dependent necroptosis.

Introduction: Natural killer (NK) cells are central to innate immune responses but they also influence adaptive immunity. Evidence suggests that NK cells are involved in protective immune responses induced by the Bacille Calmette Guerin (BCG) vaccine. In cattle, vaccination with BCG provides significant protection against infection with Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB). Bovine NK cells were previously shown to traffic from BCG vaccination sites in afferent lymph, and to be activated reciprocally through interactions with dendritic cells (DC) to drive high-level interferon gamma secretion. To further define roles for bovine NK cells in the induction of BCG vaccine-mediated immunity, we examined alterations in their frequency, location, and aggregation in lymph nodes (LN) draining immunization sites.

Materials and methods: Calves were either not vaccinated, vaccinated with BCG once, or were re-vaccinated. The frequency and localization of NK cells in draining LN was examined by immunohistochemistry and immunofluorescence, and statistical analyses of imaging outputs were performed.

Results: While increased numbers of NK cells were found in BCG-draining LN, there were no significant alterations in location, nor the clustering or aggregation of NK cells. Re-vaccination with BCG had little impact on NK cell numbers or location.

Conclusion: BCG vaccination induced changes in NK cell frequency in bovine LN. Further studies of NK cell function and co-localization with subsets of DC and T cells will be important to define the roles of these cells in the induction of protective immunity in bTB.

Introduction: The fluoroquinolone levofloxacin is often selected for use prophylactically as well as during respiratory infections. However, studies on how these antibiotics may alter innate immunity, as opposed to their bactericidal activity, are limited.

Materials & methods: We employed a murine model of therapeutically relevant antibiotic dosing to investigate the effect of prophylactic levofloxacin treatment on innate immunity.

Results: We observed mild pathology at the barrier sites of both the lung and colon in terms of alveolar space and goblet cell numbers, respectively. Although we saw no alteration in lung immune populations of neutrophils, eosinophils, or dendritic cells, we did see heightened expression of macrophage inducible nitric oxide synthase (iNOS). Interestingly this was only present in the shorter-lived CD206- interstitial macrophage subset and not observed in the long-lived resident alveolar population. Within the large intestine levofloxacin also targeted iNOS expression in the shorter-lived TIM4-CD4+ population but conversely inhibiting expression in the microbially rich colon. We therefore utilized the bone marrow-derived macrophage system, devoid of microbial interactions and demonstrated that levofloxacin had a direct effect on driving iNOS expression and increasing phagocytosis but only when present in developing macrophages and not mature macrophage populations. Our macrophage observations were replicated in ciprofloxacin, but not doxycycline-treated animals, indicating a fluoroquinolone specific action. Mechanistically, fluoroquinolone treatment was associated with mitochondrial hyperpolarization, indicating a direct alteration of macrophage immunity via off target effects.

Conclusion: Collectively, this study demonstrates a direct action of fluoroquinolones on macrophage immunity, which should be considered when selecting antibiotics for tissue specific and prophylactic use.