Identification of a previously unrecognized polypeptide associated with lymphocyte function associated antigen one (LFA-1).

In lymphocyte function associated antigen one (LFA-1) preparations from metabolically labeled lymphocytes we have observed a new polypeptide component of 86-kilodalton additional to the already described alpha- and beta-chains. This chain is cosynthesized with the alpha- and beta-chains and can be covalently cross-linked with them, resulting in a three-chain complex. This complex is recognized by the H35-89.9 anti-LFA-1 monoclonal antibody. Cleveland peptide mapping analysis indicates that the new chain is structurally different from the alpha- and beta-chains of the LFA-1 complex. The chain has been observed in B-cells as well as in T-cells. Labeling properties of the 86-kilodalton chain suggest that this molecule is not exposed on the membrane.