A monoclonal antibody (anti-Tac) reactive with activated and functionally mature human T cells. II. Expression of Tac antigen on activated cytotoxic killer T cells, suppressor cells, and on one of two types of helper T cells.

Abstract

A monoclonal antibody termed anti-Tac antibody, which reacts with human activated T cells, was functionally characterized in this study. T cells reactive with anti-Tac antibody [Tac (+)] were tested for their helper cell and suppressor cell activity in PWM-induced Ig production and for cytotoxic killer cell activity induced by a mixed leukocyte culture. Con A-stimulated T cells were depleted of Tac (+) cells by treatment with anti-Tac antibody and complement, and Con A-stimulated T cells were also separated into Tac (+) and Tac (−) cell populations by a Staphylococcal Protein A (SPA)-coated bovine red blood cell (BRBC) rosette technique. Con A-induced suppressor cell activity for PWM-induced Ig production was contained in the Tac (+) cell population but not in the Tac (−) cell population. T cells precultured with PWM and fractionated into Tac (+) and Tac (−) cell populations by a SPA-coated BRBC rosette method were also studied for helper and suppressor cell activity in a PWM-induced Ig production system. PWM-activated Tac (+) cells showed both radioresistant helper cell activity and radiosensitive suppressor cell activity. On the other hand, Tac (−) cells showed only helper cell activity. This helper activity was reduced after 2000 R irradiation. Tac (+) T cells separated from peripheral blood mononuclear cells after in vitro allosensitization showed specific cytotoxic killer cell activity against allogeneic cells, whereas Tac (−) cells did not have this function. These studies demonstrate that anti-Tac monoclonal antibody can define activated and functionally mature human T cells and also can be used to differentiate 2 different types of helper T cells, Tac (+) radioresistant and Tac (−) T cells that were more radiosensitive.