Peyer's patches: organizing B‐cell responses at the intestinal frontier

<jats:title>Summary</jats:title><jats:p>Secondary lymphoid tissues share the important function of bringing together antigens and rare antigen‐specific lymphocytes to foster induction of adaptive immune responses. Peyer's patches (<jats:styled-content style="fixed-case">PP</jats:styled-content>s) are unique compared to other secondary lymphoid tissues in their continual exposure to an enormous diversity of microbiome‐ and food‐derived antigens and in the types of pathogens they encounter. Antigens are delivered to <jats:styled-content style="fixed-case">PP</jats:styled-content>s by specialized microfold (M) epithelial cells and they may be captured and presented by resident dendritic cells (<jats:styled-content style="fixed-case">DC</jats:styled-content>s). In accord with their state of chronic microbial antigen exposure, <jats:styled-content style="fixed-case">PP</jats:styled-content>s exhibit continual germinal center (<jats:styled-content style="fixed-case">GC</jats:styled-content>) activity. These <jats:styled-content style="fixed-case">GC</jats:styled-content>s not only contribute to the generation of B cells and plasma cells producing somatically mutated gut antigen‐specific IgA antibodies but have also been suggested to support non‐specific antigen diversification of the B‐cell repertoire. Here, we review current understanding of how <jats:styled-content style="fixed-case">PP</jats:styled-content>s foster B‐cell encounters with antigen, how they favor isotype switching to the secretory IgA isotype, and how their <jats:styled-content style="fixed-case">GC</jats:styled-content> responses may uniquely contribute to mucosal immunity.</jats:p>