Indigenous opportunistic bacteria inhabit mammalian gut-associated lymphoid tissues for mucosal antibody-mediated symbiosis (39.11)

Abstract The indigenous bacteria of the gastrointestinal (GI) tract create natural cohabitation niches together with mucosal antibodies (Abs) such as secretory IgA (S-IgA). However, the nature of this symbiosis is still not well understood. Here we report that opportunistic bacteria, mostly Alcaligenes spp., specifically inhabit the gut-associated lymphoid tissues (GALT), namely Peyer's patches (PPs) and isolated lymphoid follicles (ILFs) of naive, specific-pathogen-free (SPF) but not germ-free (GF) mice. Consistent with this result, antigen-specific Ab-producing cells are present in the mucosal (e.g., PPs) but not systemic compartment (e.g., spleen). In the absence of antigen-specific mucosal Abs in PPs, intra-tissue inhabited Alcaligenes were greatly diminished. Thus, Alcaligenes uniquely inhabits PPs by inducing PP antigen-specific Ab production; this creates an optimal symbiotic environment on the interior of PPs.