Selective breeding programs aim to increase amphibian resilience to Batrachochytrium spp. infections. A suggested course of action for minimizing the effects of chytridiomycosis, a fungal disease, is in place. Chytridiomycosis tolerance and resistance are defined, along with presented evidence of tolerance variation, and explored are the resulting epidemiological, ecological, and evolutionary implications of this tolerance. Exposure risks and environmental mitigation of infection burdens heavily confound resistance and tolerance mechanisms; chytridiomycosis's defining feature is variability in constitutive, not adaptive, resistance. Tolerance's epidemiological impact is significant in propelling and maintaining pathogen spread. Tolerance's heterogeneity forces ecological trade-offs, and natural selection favoring resistance and tolerance is possibly reduced. Developing a broader understanding of infection tolerance expands our ability to lessen the continuing impacts of infectious diseases like chytridiomycosis. The theme issue 'Amphibian immunity stress, disease and ecoimmunology' encompasses this article.

Exposure to microbes in early life, as indicated by the immune equilibrium model, preconditions the immune system for efficient pathogen responses later in life. Although recent studies, using gnotobiotic (germ-free) model organisms, offer evidence for this theory, a practical model system to investigate the influence of the microbiome on immune system development is presently unavailable. Using the amphibian Xenopus laevis, this study investigated the microbiome's contribution to larval development and its subsequent impact on susceptibility to infectious diseases. During embryonic and larval phases, experimental microbiome reductions diminished microbial richness, diversity, and altered tadpole community composition before metamorphosis. NMD670 concentration Furthermore, our antimicrobial treatments demonstrated minimal adverse effects on larval development, body condition, or survival to metamorphosis. Contrary to our predictions, our antimicrobial treatments failed to affect the susceptibility of adult amphibians to the deadly Batrachochytrium dendrobatidis (Bd) fungal pathogen. Even though our treatments to diminish the microbiome during early development in X. laevis did not have a decisive role in shaping susceptibility to Bd-caused disease, they nonetheless demonstrate the considerable benefit of a gnotobiotic amphibian model for future immunology research. The theme issue 'Amphibian immunity stress, disease and ecoimmunology' includes this article.

Vertebrate immune systems, including those of amphibians, are bolstered by the vital role of macrophage (M)-lineage cells. Across vertebrate species, the process of M differentiation and its associated functions hinge on the activation of the colony-stimulating factor-1 (CSF1) receptor by the cytokines CSF1 and interleukin-34 (IL34). Molecular Diagnostics Following differentiation with CSF1 and IL34, the amphibian (Xenopus laevis) Ms cells display unique and separate morphologies, gene expression patterns, and functionalities. Significantly, the shared ancestry of mammalian macrophages (Ms) and dendritic cells (DCs) is evident, dendritic cells (DCs) being reliant on FMS-like tyrosine kinase 3 ligand (FLT3L) for maturation, a notable similarity shared with X. laevis IL34-Ms' resemblance to mammalian dendritic cells. We presently juxtaposed X. laevis CSF1- and IL34-Ms with FLT3L-generated X. laevis DCs for comparative assessment. Our investigation into transcriptional and functional aspects highlighted a substantial congruence between frog IL34-Ms and FLT3L-DCs, relative to CSF1-Ms, specifically regarding their transcriptional profiles and functional capacities. X. laevis CSF1-Ms exhibited lower surface expression of major histocompatibility complex (MHC) class I molecules compared to IL34-Ms and FLT3L-DCs, which showed a significantly higher MHC class I expression, although MHC class II expression remained similar. This difference in MHC expression translated to a greater capacity for eliciting mixed leucocyte responses in vitro and inducing more effective immune responses against Mycobacterium marinum re-exposure in vivo. Investigating non-mammalian myelopoiesis, employing methods analogous to those described here, will provide novel perspectives on the evolutionary conservation and diversification of M and DC functional specializations. Part of the special publication, 'Amphibian immunity stress, disease and ecoimmunology', is this article.

Naive multi-host communities are comprised of species exhibiting diverse capacities in the maintenance, transmission, and amplification of novel pathogens; hence, we expect different species to assume distinct roles during the onset of infectious diseases. Ascribing specific functions to these roles in wild animal communities proves challenging, owing to the unforeseen nature of most disease emergence events. Our investigation into the emergence of Batrachochytrium dendrobatidis (Bd) within a diverse tropical amphibian community relied on field-collected data to assess how species-specific characteristics impacted exposure, the likelihood of infection, and the intensity of the pathogen. Our study confirmed a positive relationship between infection prevalence and intensity at the species level during the outbreak and ecological traits frequently seen as indicators of decline. Key hosts in this community, which were disproportionately involved in transmission dynamics, revealed a disease response pattern reflecting phylogenetic history, associated with greater pathogen exposure resulting from shared life-history traits. Our investigation establishes a framework that can be applied to conservation, focusing on identifying species essential to disease patterns during enzootic phases, a critical step before releasing amphibians into their native ranges. Reintroduction of supersensitive hosts lacking the capacity to overcome infections will limit the success of conservation programs by leading to intensified community-level disease. The article you are reading is part of a dedicated issue on the topic of 'Amphibian immunity stress, disease, and ecoimmunology'.

Improved comprehension of the dynamic relationship between host-microbiome interactions and anthropogenic environmental alterations, as well as their influence on pathogenic infections, is critical to advancing our understanding of stress-related disease development. Our study explored the consequences of rising salinity in freshwater bodies, for instance. In larval wood frogs (Rana sylvatica), road de-icing salt runoff, triggering an uptick in nutritional algae, directly modulated gut bacterial assembly, host physiology, and susceptibility to ranavirus. Enhanced salinity levels and the addition of algae to a foundational larval diet resulted in both accelerated larval growth and elevated ranavirus concentrations. Larvae receiving algae, surprisingly, did not exhibit increased kidney corticosterone levels, faster growth, or weight loss following infection, in contrast to the larvae fed a standard diet. Therefore, the incorporation of algae counteracted a potentially harmful stress reaction to infection, as observed in prior studies using this model. Immunohistochemistry Gut bacterial diversity was also diminished by the addition of algae. Algae-supplemented treatments exhibited a higher relative abundance of Firmicutes, correlating with increased growth and fat deposition commonly seen in mammals. This trend may potentially explain the diminished stress response to infection through adjustments in the host's metabolism and endocrine functions. Through our study, we formulate mechanistic hypotheses about the microbiome's role in modulating host responses to infection, hypotheses that future experiments within this host-pathogen system can evaluate. This article is featured in a thematic issue concerning 'Amphibian immunity stress, disease and ecoimmunology'.

Among all vertebrate groups, including birds and mammals, amphibians, as a class of vertebrates, exhibit a higher susceptibility to decline or extinction. Habitat destruction, the encroachment of invasive species, unsustainable human activity, the release of toxic chemicals, and the appearance of new diseases contribute to a substantial list of environmental threats. Climate change's capricious impacts on temperature and rainfall represent an added threat. To survive these intertwined threats, amphibian immune systems must operate with considerable efficiency and effectiveness. The current body of knowledge regarding amphibian responses to natural stressors, including heat and desiccation, and the limited research on their immune responses under these stresses, is summarized in this review. Generally, the present scientific literature indicates that dehydration and heat stress can stimulate the hypothalamic-pituitary-adrenal axis, potentially suppressing some innate and lymphocyte-mediated immunological reactions. Changes in temperature can disrupt the microbial balance in amphibian skin and gut, causing dysbiosis and a diminished capacity for defending against pathogens. This article contributes to the broader theme of 'Amphibian immunity stress, disease, and ecoimmunology'.

The salamander-targeting chytrid fungus, Batrachochytrium salamandrivorans (Bsal), poses a significant threat to the biodiversity of salamanders. Glucocorticoid hormones (GCs) are suspected to be one element within the set of factors contributing to Bsal susceptibility. The well-established connection between glucocorticoids (GCs) and immunity/disease susceptibility in mammals contrasts with the relatively sparse information available for similar studies in non-mammalian groups, including salamanders. Eastern newts (Notophthalmus viridescens) were used to empirically evaluate the hypothesis that glucocorticoids affect the immunological mechanisms of salamanders. We initially ascertained the dosage needed to elevate corticosterone (CORT, the primary glucocorticoid in amphibians) to physiologically significant levels. Immunity markers (neutrophil lymphocyte ratios, plasma bacterial killing ability (BKA), skin microbiome, splenocytes, melanomacrophage centers (MMCs)) and overall health were evaluated in newts after treatment with CORT or an oil vehicle control.