Monoclonal anti-Lyt-2.2 antibody blocks lectin-dependent cellular cytotoxicity of H-2-negative target cells

The hypothesis that blocking of cytotoxic T lymphocyte (CTL)-mediated cytolysis with anti-Lyt-2 antibodies acts at the level of inhibiting the interaction of the Lyt-2-bearing structure with H-2 class I molecules was tested. In agreement with the findings of others, purified anti-Lyt-2.2 inhibited both antigen-specific lysis and lectin- dependent cellular cytotoxicity (LDCC). LDCC of H-2-positive and H-2- negative target cells was similarly inhibited by this antibody. As expected, this effect was specific for CTL expressing the Lyt-2.2 allele, in contrast to blocking with a rat monoclonal antibody to the murine LFA-1 antigen. The implications of this finding for the function of the Lyt-2 antigen in CTL-target cell interaction are discussed.