Modulation of in vitro immune responses by monoclonal antibody to T200 antigen

The effects of monoclonal antibody to the T200 antigen on murine mixed-lymphocyte cultures (MLC) and on the generation of alloreactive cytotoxic T lymphocytes (CTL) are investigated. Addition of monoclonal anti-T200 without complement to MLC results in a late suppression of the proliferative response preceded in some cases by an early enhancement. These modulations require the presence of allogeneic stimulator cells; no effects are seen when antibody is added to responders alone. A similar effect is seen on the generation of CTL. Compared to controls without antibody, cultures carried out in the presence of anti-T200 show reduced levels of cytotoxicity measured against allogeneic targets by Day 5. The kinetics of the suppressive effects differ from those seen with anti-Lyt-2, and no suppressive effects are seen with monoclonal antibodies to other cell surface molecules.