CRTAM shapes the microbiota and enhances the severity of gut infection.

Abstract

Abstract Gut lymphocytes and the microbiota establish a reciprocal relationship that tunes the host immune response. For example, the gut microbiota is required for T helper (Th)-17 cell differentiation; Th17 cytokines, in turn, stimulate the intestinal epithelium to produce antimicrobial proteins that control the gut microbiota. Residency and maintenance of T cells in the gut is controlled by Class I-restricted T cell-associated molecule (CRTAM). We thus evaluated whether CRTAM influences the gut microbiota composition. We found that CRTAM expression caused a shift in several members of the gut microbiota under homeostatic conditions. As the gut microbiota and T cells contribute to host defense against intestinal pathogens, we tested whether CRTAM plays a role during infection with the enteric pathogen Salmonella. We found lower levels of Salmonella colonization in the gut of Crtam−/− mice, along with lower expression of the Th17 cytokines Il17 and Il22 in the cecum. Salmonella-infected Crtam−/− mice exhibited fewer gut T cells and IL-17-producing cells. To investigate whether the altered gut microbiota composition of Crtam−/− mice influenced the host response to infection, we transplanted the fecal microbiota from WT or Crtam−/− littermate mice into germ-free mice, and then infected the mice with Salmonella. Relative to mice transplanted with “WT” fecal microbiota, mice transplanted with “Crtam−/−” microbiota exhibited lower numbers of T cells and IL-17-producing cells in the gut upon infection. Our results thus suggest an interplay between CRTAM expression and the gut microbiota, which ultimately impacts the mucosal immune system and the host response to enteric pathogens.