The effect of in vitro T lymphocyte depletion on generation of IL2-activated cytotoxic cells

The effect of immunocompetent lymphocyte depletion on precursors and effector cells of IL2 activated non-MHC restricted cytotoxic cells (LAK) generated from bone marrow (BM) or peripheral blood was investigated. Lymphocyte depletion was carried out by using Campath-1, a monoclonal rat anti-human lymphocyte antibody recognizing CDW52, that binds human complement and is used routinely in clinical bone marrow transplantation (BMT). The results indicate that LAK precursors derived from BM cells are sensitive to Campath-1 treatment, while a variable degree of sensitivity was demonstrated in LAK precursor cells derived from peripheral blood. In contrast, effector LAK cells generated in vitro were shown to be resistant to treatment with Campath-1 and complement. We hypothesize that if indeed IL2-dependent non-MHC restricted cytotoxic cells play a role in vivo in the immediate post-BMT period, a T lymphocyte depletion procedure such as the Campath-1 may have the capacity to reduce, at least temporarily, the graft-versus-leukemia effects mediated by such anti-tumor effector mechanisms.