Gut microbes drive maturation of host's immune system. Not every microbe is able to do it, however. So what microbial qualities determines its impact on host?
New paper in journal Cell has revealed a simple rule of thumb: microbes that could attach themselves to gut epithelial cells drove induction of local Th17 cells and IgA. Interestingly this microbial quality found to be species-specific.
Initially, the authors showed that monocolonization of germ-free mice or rats with endogenous segmented filamentous bacteria (mouse-SFB and rat-SFB) induced Th17 cells in a species-specific manner (mouse data are shown here ).
Ex vivo stimulation of lamina propria cells with autoclaved fecal antigens (A/C) showed that IL-17 secretion and IgA production were correlated with species-specific access to SFB antigens in the gut.
Additional experiments with WT microbes or microbes lacking adhesion molecules confirmed that epithelial adhesion determined IL-17/IgA production.
In summary, these results indicate that direct adhesion to gut epithelial cells is necessary pre-condition for local immune response induction. Mechanistically, this adhesion by microbes induces production of serum amyloid A (SAA) that primed local T cells for Th17 phenotype.