Mucosal Immunity

Zika virus RNA is frequently detected in the semen of men after Zika virus infection. To learn more about persistence of viruses in genital fluids, we searched PubMed for relevant articles. We found evidence that 27 viruses, across a broad range of virus families, can be found in human semen.

Large quantities of immunoglobulin A (IgA) are constitutively secreted by intestinal plasma cells to coat and contain the commensal microbiota, yet the specificity of these antibodies remains elusive. Here, we profiled the reactivities of single murine IgA plasma cells by cloning and characterizing large numbers of monoclonal antibodies. IgAs were not specific to individual bacterial taxa but rather polyreactive, with broad reactivity to a diverse but defined subset of microbiota. These antibodies arose at low frequencies among naïve B cells, and were selected into the IgA repertoire upon recirculation in Peyer’s patches. This selection process occurred independent of microbiota or dietary antigens. Furthermore, while some IgAs acquired somatic mutations, these did not substantially influence their reactivity. These findings reveal an endogenous mechanism driving homeostatic production of polyreactive IgAs with innate specificity to microbiota.

Type 1 diabetes has a multifactorial etiology. Lehuen and colleagues demonstrate that MAIT cells serve both positive roles and negative roles in type 1 diabetes by maintaining gut integrity and limiting pancreatic inflammation but also directly destroying [beta]-cells.

CD4+CD8αα+ double-positive intraepithelial lymphocytes (DP IELs) are a recently discovered class of intestinal T cells believed to take part in a variety of immune responses, including oral tolerance. These cells are absent in germ-free mice, but the mechanisms driving their development are unclear. Cervantes-Barragan et al. found that a particular species of probiotic bacteria, Lactobacillus reuteri , induces DP IELs. This does not occur by stimulating the immune system directly. Instead, L. reuteri generates a specific derivative of dietary tryptophan that promotes differentiation of DP IEL precursors. These findings underscore the delicate interplay between benign bacteria, diet, and gut health.

Science , this issue p. [806][1]

[1]: /lookup/doi/10.1126/science.aah5825

Infection or inflammation of the skin recruits effector CD8+ T cells that enter the epidermis and form populations of long-lived tissue-resident memory T (TRM) cells. These skin TRM cells migrate within the constrained epidermal environment by extending multiple dynamic dendritic projections and squeezing between keratinocytes to survey the tissue for pathogens. In this study, we examined the signals required for this distinctive mode of T cell migration by inhibiting key cytoskeletal components and performing intravital two-photon microscopy to visualize TRM cell behavior. We found that TRM cell motility and dendrite formation required an intact actomyosin cytoskeleton and the Rho-associated coiled-coil containing kinases. We also identified an essential role for microtubules for maintaining skin TRM cell shape and cellular integrity. We reveal a role for pertussis toxin–sensitive signaling for TRM cell dendritic morphology and migration that is independent of CXCR3 or CXCR6, or the skin-selective chemokine receptors CCR10 and CCR8. However, we found that CXCR6 and CCR10 expression by CD8+ T cells was required for the optimal formation of memory T cell populations, in particular TRM cell populations in the skin.

Composed of trillions of individual microbes, the human gut microbiota has adapted to the uniquely diverse environments found in the human intestine. Quickly responding to the variances in the ingested food, the microbiota interacts with the host via reciprocal biochemical signaling to coordinate the exchange of nutrients and proper immune function. Host and microbiota function as a unit which guards its balance against invasion by potential pathogens and which undergoes natural selection. Disturbance of the microbiota composition, or dysbiosis, is often associated with human disease, indicating that, while there seems to be no unique optimal composition of the gut microbiota, a balanced community is crucial for human health. Emerging knowledge of the ecology of the microbiota-host synergy will have an impact on how we implement antibiotic treatment in therapeutics and prophylaxis and how we will consider alternative strategies of global remodeling of the microbiota such as faecal transplants. Here we examine the microbiota-human host relationship from the perspective of the microbial community dynamics.