CD4(+) T lymphocytes as a primary cellular target for BAT mAb stimulation

BAT is a monoclonal antibody (mAb) produced against membranes of a human Bu rkitt lymphoma cell line (Daudi) that was selected for its ability to stimu late lymphocyte proliferation. BAT manifests anti-tumor properties in mice bearing a variety of murine tumors. BAT also induced regression of human tu mors inoculated into SCID mice that had been engrafted with human lymphocyt es, The anti-tumor activity of BAT was related to its immune stimulatory pr operties. Previous data indicated that T lymphocytes and NK cells mediate i n vivo the anti-tumor activity. In order to define the primary target cell for BAT stimulatory activity, the in vitro stimulatory effect of BAT on pur ified lymphocyte subpopulations was investigated. Human CD4(+), CD8(+) T ce lls and CD56(+) NK cells were purified and their in vitro response to BAT w as investigated, Results indicate that BAT selectively stimulated CD4(+) ce lls as assessed by proliferation and secretion of IFN-gamma, FAGS analysis has also revealed a selective increase in BAT antigen on CD4+ T cells that were cultured with BAT antibody. The effector cells that mediate BAT-induce d tumor eradication may, however, be distinct from those that serve as the primary cellular target of the antibody, Cytokines such as IFN-gamma that a re produced by CD4(+) cells may be involved in activation of additional cel l types that may be involved in tumor destruction.