Critical role for beta7 integrins in formation of the gut-associated lymphoid tissue.

Immune defence against pathogens entering the gut is accomplished by lymphocytes in the gut-associated lymphoid tissue (GALT), a major compartment of the immune system. The GALT, comprising Peyer's patches, lamina propria lymphocytes and intra-epithelial lymphocytes of the intestine, is populated by lymphocytes that migrate there from the vasculature. Here we report that, in mice deficient for the beta7 integrin subfamily of adhesion molecules, the formation of the GALT is severely impaired. This is probably due to a failure of beta7-/- lymphocytes to arrest and adhere to the vasculature at the site of transmigration into the GALT.