The Journal of Immunology, Vol 127, Issue 4 1485-1489, Copyright © 1981 by American Association of Immunologists

ARTICLES

Effects of gamma-irradiation on lymphocyte subpopulations participating in the development of the cytotoxic T lymphocyte response

BM Susskind and RB Faanes

Differences in radiosensitivity among lymphocyte subpopulations involved in generating allogeneic cytotoxic T lymphocyte (CTL) responses were studied. Gamma irradiated splenic lymphocytes from C57BL/6 mice (B6, H-2b) were stimulated in vitro with DBA/2 (H-2d) spleen cells or the DBA/2 mastocytoma, P815. Limiting dilution analysis indicated that the cytotoxic T lymphocyte effector cells (CTLe) for either antigen arose from the same pool of cytotoxic T lymphocyte precursors (CTLp), and that the D37 value of the B6 anti-H-2d CTLp was approximately 165 R. In mixed lymphocyte cultures, however, differential effects of irradiation were seen between the 2 antigens in the ability of irradiated responder B6 spleen cells to generate CTLe. For induction of cytotoxic activity against DBA/2 splenocytes, the CTLp was the most radiosensitive component of the response, whereas the generation of a cytotoxic response against P815 was limited by the radiosensitivity of an Lyt-1 T helper cell (D37 approximately 85 R). The radiosensitive Lyt-1 cell could be replaced by mixed lymphocyte reaction supernatants or semipurified interleukin 2 (IL-2) from Con A- stimulated murine spleen cells. The requiremet of B6 anti-H-2d CTLp for a radiosensitive accessory cell in the CTL response against P815, in contrast with their activation by DBA/2 splenocytes, may center on the fact that the tumor cells do not possess Ia antigens.