CTLA-4 (CD152) Inhibits the Specific Lysis Mediated by Human Cytolytic T Lymphocytes in a Clonally Distributed Fashion

Since the functional outcome of effector T lymphocytes depends on a balance between activatory and inhibitory receptors, we studied the ability of CTLA-4 (CD152) to inhibit the cytolytic function of CTL. In 22 TCR alpha/beta+ CD3+ 8+ CTL clones, activation induced by anti-CD3, anti-CD28, or anti-CD2 mAb was inhibited by anti-CD152 mAb in a redirected killing assay. In eight clones inhibition was >40%, in 10 it ranged between 20-40%, and in four it was 40% increment of target cell lysis was achieved in three of eight clones studied. Since it is not equally shared by all CTL clones, this feature also appears to be clonally distributed.