Peyer's patch-specific lymphocyte homing receptors consists of a VLA-4-like α chain associated with either of two integrin β chains, one of which is novel

Abstract

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 α subunit (α(4m)) analogous to the α chain of the human integrin molecule VLA-4. Here we show that the LPAM-1 β subunit (βp) is immunochemically and biochemically distinct from previously defined integrin β subunits, suggesting that β(p) represents a novel integrin β subunit. Depending on the cellular source two alternative β subunits, β(p) and integrin β1, can be isolated in association with α(4m). Therefore, α(4m) is the common subunit of the unique integrin LPAM-1 (α(4m)β(p)) and of the heterodimer LPAM-2 (α(4m)β1), 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.