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Immunoglobulin (Ig) A secretion into the intestinal lumen is an important immune mechanism of the gastrointestinal (GI) tract. B cells proliferate and differentiate into IgA-secreting plasma cells (PC) within lymphoid organs then migrate directly into the intestinal lamina propria. We aimed to elucidate the in vivo role of the mucosal addressin cell-adhesion molecule-1 (MAdCAM-1), which is constitutively expressed in the GI-associated lymphoid tissue, in B-cell migration.
We generated MAdCAM-1-deficient mice (MAdCAM(Delta)) and evaluated the B-cell compartment of the GI-associated lymphoid tissue. We also assessed PC migration to the small intestine and the intestinal immune response after oral immunization.
In MAdCAM(Delta) mice, the size of Peyer's patches was drastically reduced, compared with that of wild-type mice; this difference was detectable by 3 days after birth, indicating that MAdCAM-1 is dispensable for embryonic Peyer's patch development but mediates recruitment of lymphocytes into this lymphoid organ at later stages. Moreover, antigen-specific, IgA-positive PC were severely compromised in their migration to the small intestine; accordingly, there was a reduced number of IgA-secreting PC in the lamina propria of the small intestine. The MAdCAM(Delta) mice were unable to mount a normal intestinal IgA response after oral immunization with cholera toxin.
These data provide in vivo evidence that MAdCAM-1 is required for the localization and function of IgA-secreting PC in the intestine.