T lymphocyte recognition of alloantigen in vitro. II. Significance of Fc receptor positive and negative responder T cells in the generation of cytotoxic T lymphocytes from normal or immune mice.

The present experiments were carried out in order to answer the question whether the precursor T cells of cytotoxic T lymphocytes (PCTL) are Fc receptor positive (FcR+), Fc receptor negative (FcR-), or both. The data show that cytotoxic T lymphocytes (CTL) can be generated in vitro from both FcR+ and FcR- PCTL. Furthermore, we investigated if the function of FcR+ and FcR- CTL differed in the allograft response in vitro. Qualitatively, FcR- PCTL differentiate into FcR- CTL only, whereas FcR+ PCTL differentiate into both FcR+ and FcR- CTL. However, quantitatively, CTL generated from FcR- PCTL display a higher T cell mediated cytotoxicity than CTL generated from FcR+ PCTL. Mixing experiments indicate that FcR+ T cells regulate the differentiation of FcR- PCTL into CTL. These conclusions hold true for PCTL in both normal and memory responder cell populations.