In vivo separation of two classes of T cells as determined by negative selection after the injection of UV-treated allogeneic lymphoid cells.

Negative selection occurred when gamma-irradiated lymphoid cells of rat strain PVG were injected intravenously into strain Fischer rats, which differ from PVG rats at the major histocompatibility complex. By 48 hr after injection, thoracic duct lymphocytes (TDL) from these animals failed to proliferate or generate cytotoxic T lymphocytes (CTL) in vitro in response to gamma-irradiated PVG lymphoid cells. Responses to cells of a third rat strain were unaffected. By about 6 days after antigen injection, positive selection had occurred, as shown by enhanced responses to gamma-irradiated PVG cells in the same assays. Ultraviolet-irradiated strain PVG populations were tested in the same way. They differed from gamma-irradiated PVG cells in that they failed to induce proliferation or stimulate CTL in vitro. TDL from Fischer rats injected with UV-irradiated PVG cells failed to proliferate or generate CTL in response to gamma-irradiated PVG cells in vitro. The CTL response of TDL from rats injected with UV-irradiated cells was restored by the addition of supernatant factor(s) from concanavalin A-stimulated lymphoid cells (ConA SnF). Therefore, CTL precursors did not undergo negative selection after injection of UV-treated cells. There was also no detectable positive selection 6 days after injection of UV-treated cells. These experiments show that it is possible to separate two populations of T cells in vivo by the injection of UV-irradiated allogeneic lymphoid cells. One population incorporates [3H]thymidine early in an allogeneic response in vitro, the other expresses cytotoxic activity only after the addition of ConA SnF in vitro. The first population can replace the requirement for ConA SnF by the CTL population.