Fig. 3.

Recirculating B cells coordinate IgA responses in GALT. Antigen experienced B cell are capable of re-entering germinal center (GC). Red dotted lines schematically illustrate B cell migratory routes. GALT#1 and GALT #2 are displayed to represent two different GALT structures such as Peyer’s patches or isolated lymphoid follicles. Different members of the microbiota might have been taken up into GALT and create distinct antigenic environments. We speculate that repeated rounds of selection in different GC, putatively including different antigens, might contribute to the generation of affinity matured cross-species reactive antibodies.