Immunosuppressive ATS. V. Analysis of the effect of anti-thymocyte serum on T lymphocyte subsets.

The effect of anti-thymocyte serum (ATS) on functional T cell subsets within the immunoregulatory network was examined. We found that low doses of ATS depleted the IL 2-producing subset of T helper cells and higher doses of antiserum also eliminated cytotoxic precursors. It was estimated that a standard low dose of ATS, which reduced T helper cells 80-fold, depleted cytotoxic precursors only about four-fold. The data indicate that ATS acts on different T cell subsets in a dose-dependent fashion and suggest that monoclonal antibodies might be used to preferentially deplete specific T cell subpopulations. Two monoclonal rat anti-mouse Lyt sera, however, proved ineffective in inducing functional changes in vivo, although an alloantiserum to Lyt1.1 was able to reduce cell-mediated cytotoxicity in a dose-dependent fashion. The results support the feasibility of specific depletion of T cell subsets with anti-lymphoid antibodies.