Immunologic and structural relatedness of the integrin β7complex and the human intraepithelial lymphocyte antigen HML‐1

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Abstract
We recently cloned the newest human integrin β subunit, termed β7, from a cDNA library constructed from SEA‐activated T lymphocytes. In this communication, we report on the structure of the human integrin β7 protein complex determined using a rabbit anti‐β7 peptide antibody raised to an N‐terminal 22 amino acid residue sequence deduced from the human β7 subunit cDNA. The β7 subunit (M, 116 000) expressed on PHA lymphoblasts associates with asingle major α subunit (α11) that is distinct from the prominent T cell marker, integrin α4. The α11 subunit (M r 180 000 nonreduced) displays a distinctive shift in size on reduction to an apparent M r of 150 000. We show that these structural properties of the integrin β7 complex are shared with the cell surrace antigen HML‐1 found highly expressed on T cells which populate the intestinal epithelium and are proposed to be involved in mucosal immunity. Sequential immunoprecipitation and Western blotting demonstrate identity or close homology between the α11β7 and HML‐1 proteins.