Antibodies to membrane structures that distinguish suppressor/cytotoxic and helper T lymphocyte subpopulations block the mixed leukocyte reaction in man.

Abstract

Two major subsets of human T lymphocytes that are functionally analogous to the mouse Lyt-2+ and Lyt-2- subsets were defined by their expression of 2 thymus-dependent membrane antigens, Leu-2 and Leu-3. Leu-2+,3- cells have suppressor cytotoxic functions; Leu-2-,3+ cells have helper functions. The effects of adding IgG1 monoclonal anti-Leu-2 and anti-Leu-3 antibodies to the mixed leukocyte reaction (MLR) were studied. At high concentrations, each antibody partially inhibited the proliferative response of unseparated T cells and abolished the response of the isolated subset having the appropriate phenotype. An IgG1 monoclonal antibody to HLA-A2 and an IgG2a antibody to Leu-1, a pan-T antigen, failed to ihiibit the MLR. The Leu-2 and Leu-3 antigens may have a direct role in the mechanisms whereby T cells recognize and respond to alloantigen.