The tiny conductor: immune regulation via commensal organisms.

ABSTRACT

The astonishing density of microbes in the mammalian gut has raised numerous questions, including how such colonization is tolerated in an immunocompetent location. Clearly the organisms perform a beneficial role, but until now the mechanisms have been less than clear. In a recent study in Nature, Mazmanian et al. (2008) reveal the ability of specific moieties on the surface of Bacteroides fragilis to direct the host's immune response.