Innate and Adaptive Humoral Responses Coat Distinct Commensal Bacteria with Immunoglobulin A (Immunity)

Bendelac and colleagues find that homeostatic IgA responses target commensal bacteria that reside in the small intestine but exclude bacteria indigenous to the colon. Most commensals are targeted by T-independent IgA derived predominantly from the orphan B1b lineage, but atypical subsets evade T-independent responses and elicit T-dependent IgA.