Reversible Microbial Colonization of Germ-Free Mice Reveals the Dynamics of IgA Immune Responses

A Gut Feeling The mammalian gut is colonized by many nonpathogenic, commensal microbes. In order to prevent the body from mounting inappropriate immune responses to these microbes, plasma cells in the gut produce large amounts of immunoglobulin A (IgA) specific for commensal bacteria. Because of the difficulties of uncoupling IgA production from microbial colonization, how commensal bacteria shape the gut IgA response is not well understood. Hapfelmeier et al. (p. 1705 ; see the Perspective by Cerutti ) have now devised a way to get around this problem by developing a reversible system of gut bacterial colonization in mice. Commensal-specific IgA responses were able to persist for long periods of time in the…