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Sequestration of gut pathobionts in intraluminal casts, a mechanism to avoid dysregulated T cell activation by pathobionts

ABSTRACT: T cells that express the transcription factor RORg, regulatory (Treg) or conventional (Th17), are strongly influenced by intestinal symbionts. In a genetic approach to mechanisms underlying this influence, we performed a screen for microbial genes implicated, in germfree mice monocolonized with E.coli Nissle. The loss of capsule-synthesis genes impaired clonal expansion and differentiation of intestinal RORg+ T cells. Mechanistic exploration revealed that the capsule-less mutants remained able to induce specific IgA and were highly IgA-coated. They could still trigger myeloid cells, and more effectively damaged epithelial cells in vitro. Unlike wild-type microbes, capsule-less mutants were mostly engulfed in intraluminal casts, large agglomerates composed of myeloid cells extravasated into the gut lumen. We speculate that sequestration in luminal casts of potentially harmful microbes reduces the immune system’s actual exposure, preserving host-microbe equilibrium. The variable immunostimulation by microbes charted in recent years may not solely be conditioned by triggering molecules or metabolites, but also by physical limits to immunocyte exposure.

ORGANISM(S): Mus musculus

PROVIDER: GSE211049 | GEO | 2022/09/27

REPOSITORIES: GEO

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