Cloning and expression of mouse integrin β(β₇): A functional role in Peyer's patch-specific lymphocyte homing

Lymphocytes express integrin receptors, termed lymphocyte Peyer's patch high endothelial ventile (HEV) adhesion molecules (LPAMs), that mediate their organ-specific adhesion to specialized HEVs found in mucosal lymphoid organs (Peyer's patches). LPAM-1 consists of a murine integrin α₄ noncovalently associated with integrin β_P. Here, we describe the cloning and expression of a mouse cDNA encoding β_P, which is an 806-amino acid transmembrane glycoprotein. The genomic Southern blot analysis indicates that β_P is the murine homologue of human β_P. The function of α₄β₇ as a Peyer's patch-specific adhesion molecule was tested directly by expression of the murine β₇ cDNA in an α₄⁺β₇^- B-cell line or coexpression of the α₄and β₇ cDNAs in an α₄-β₇^- T-cell line. The transfected cells exhibited a new Peyer's patch-specific adhesive phenotype that could be specifically blocked by monoclonal antibodies against α₄ and β₇. Moreover, an anti-β₇ monoclonal antibody specifically blocked binding of normal lymphocytes to Peyer's patch HEV but did not inhibit their binding to peripheral lymph node HEVs, indicating that β₇ is a unique component of the Peyer's patch-specific homing receptor.