EVIDENCE FOR CELL-SURFACE ASSOCIATION OF CD2 AND LFA-1 (CD11A CD18) ON T-LYMPHOCYTES/

Previous studies have reported an association of the cell surface adhe sion molecule CD2 with the T cell receptor and with CD-CS on mouse and human T lymphocytes. In this study the association of CD2 with cell s urface molecules was investigated using cell surface biotinylation of T lymphocytes, coupled with immunoprecipitation using two CD2-specific monoclonal antibodies (mAb) (RM2-5 and 12-15) and analysis by SDS-PAG E. Although both CD2 mAb immunoprecipitated CD2 from lysates of murine lymphocytes, it was found that mAb 12-15, but not RM2-5, co-precipita ted two other molecules of 95 and 180 kDa. Subsequent studies revealed that the 95- and 180-kDa molecules were associated with a subspecies of CD2 (similar to 5%) on thymocytes, the antigen-specific T cell line D10, and splenic T cells but not B cells. Two lines of evidence were obtained consistent with the 95- and 180-kDa molecules being the beta and alpha chains of LFA-1. Firstly, an analysis of 12-15 mAb immunopre cipitates on 4-12% gels under reducing and nonreducing conditions show s that the 95- and 180-kDa molecules have a molecular weight and migra tion pattern identical to LFA-1. Secondly, depletion of LFA-1 from lys ates with LFA-1 mAb abolished the ability of CD2 mAb 12-15 to co-preci pitate the 95- and 180-kDa molecules, thereby identifying these as the beta and alpha chains of mouse LFA-1. respectively. These results pro vide evidence for the first time for an association of LFA-1 and CD2, on mouse T lymphocytes, and suggest that the association occurs with a n immunologically distinct subspecies of CD2 molecules.