TLR5 stops commensals in their tracks.

IgA antibodies help maintain intestinal immune homeostasis with resident commensal species; however, the precise mechanisms regulating IgA induction and the epitopes recognized by these antibodies remain incompletely understood. In this issue of Cell Host & Microbe, Tyler et al. (2013) demonstrate that TLR5-dependent induction of anti-flagellin antibodies prevents commensal association with the intestinal mucosa by limiting bacterial motility.