Evidence for cell surface association of CD2 and LFA‐1 (CD11a/CD18) on T lymphocytes

Abstract

Previous studies have reported an association of the cell surface adhesion molecule CD2 with the T cell receptor and with CD45 on mouse and human T lymphocytes. In this study the association of CD2 with cell surface 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‐PAGE. Although both CD2 mAb immunoprecipitated CD2 from lysates of murine lymphocytes, it was found that mAb 12–15, but not RM2–5, co‐precipitated 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 (˜ 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 β and α chains of LFA‐1. Firstly, an analysis of 12–15 mAb immunoprecipitates on 4–12% gels under reducing and nonreducing conditions shows that the 95‐ and 180‐kDa molecules have a molecular weight and migration pattern identical to LFA‐1. Secondly, depletion of LFA‐1 from lysates with LFA‐1 mAb abolished the ability of CD2 mAb 12–15 to co‐precipitate the 95‐ and 180‐kDa molecules, thereby identifying these as the β and α chains of mouse LFA‐1, respectively. These results provide evidence for the first time for an association of LFA‐1 and CD2 on mouse T lymphocytes, and suggest that the association occurs with an immunologically distinct subspecies of CD2 molecules. Show more