Peyer's patch-specific lymphocyte homing receptors consist of a VLA-4-like alpha chain associated with either of two integrin beta chains, one of which is novel.

Lymphocytes home to various lymphoid organs by adhering to and migrating through specialized high endothelial venules (HEV). The murine cell surface heterodimer LPAM-1 is involved in the homing of lymphocytes to mucosal sites (Peyer's patches). LPAM-1 has an alpha subunit (alpha 4m) analogous to the alpha chain of the human integrin molecule VLA-4. Here we show that the LPAM-1 beta subunit (beta p) is immunochemically and biochemically distinct from previously defined integrin beta subunits, suggesting that beta p represents a novel integrin beta subunit. Depending on the cellular source two alternative beta subunits, beta p and integrin beta 1, can be isolated in association with alpha 4m. Therefore, alpha 4m is the common subunit of the unique integrin LPAM-1 (alpha 4m beta p) and of the heterodimer LPAM-2 (alpha 4m beta 1), which is analogous to VLA-4. Antibody-blocking experiments suggest that, in addition to LPAM-1, LPAM-2 is also involved in the organ-specific adhesion of lymphocytes to Peyer's patch HEV.