Gut lymphocyte migration: we are halfway ‘home’

The gastrointestinal immune system consists of immune cells in organized gut-associated lymphoreticular tissues (GALT) and diffuse lamina propria, which give rise to mucosal secretory IgA antibody responses. A recent study showed that the retinoic acid produced by GALT dendritic cells (DCs) imprints B cells for gut homing. Surprisingly, GALT DCs, together with interleukin-5 (IL-5) and IL-6, also provided a milieu for both B cell switching to IgA and IgA synthesis.