Membrane glycoprotein p150,95 of human cytotoxic T cell clone is involved in conjugate formation with target cells.

The p150,95 heterodimer, one of three members of the leukocyte function associated antigen (LFA) family, is expressed by monocytes, granulocytes, NK cells, and a small percentage of lymphocytes. We now report that the p150,95 glycoprotein is expressed by some cytotoxic T cell clones and that it is involved in cell-mediated cytolysis by these clones. Two CTL clones, clone JS-93 (CD3+ CD4+ CD8-) and clone JS-102 (CD3+ CD4- CD8+) expressed high levels of p150,95 and were shown to be specifically directed against HLA-DR and HLA-A2, respectively. Immunoprecipitations followed by two-dimensional gel electrophoresis demonstrated no heterogeneity in the p150,95 molecule isolated from both clones. Furthermore, we demonstrated that monoclonal antibodies (moab) directed against p150,95 could inhibit the cytotoxic activity of both clone JS-93 and clone JS-102 (50% and 47%, respectively). Single cell assays revealed the inhibition to occur at the level of conjugate formation rather than at the level of the lethal hit. Similar results were obtained with moab directed against LFA-1 (p170,95). The capacity of the moab directed against LFA-1 and p150,95 to inhibit CTL activity and conjugate formation were additive, resulting in a similar percentage of inhibition as found with moab directed against the common beta-chain of these molecules. It is concluded that at least some CTL clones express the p150,95 antigen at their cell surface, and that this molecule, like LFA-1, acts at the level of conjugate formation between effector and target cells.