Antigen stimulation of cytolytic T lymphocyte precursors: minimal requirements for growth and acquisition of cytolytic activity.

Minimal requirements for growth and acquisition of cytolytic activity by alloantigen-stimulated cytolytic T lymphocyte precursors (CTL-P) have been investigated. CTL-P from C57BL/6 spleen were purified by staining with monoclonal anti-Lyt-2 antibodies followed by positive selection on a fluorescence-activated cell sorter. Microcultures containing 2000 purified Lyt-2+ cells were set up with irradiated P815 (DBA/2 mastocytoma) stimulating cells and pure interleukin 2 obtained by recombinant DNA technology (rIL2). Proliferation and generation of antigen-specific cytolytic activity were observed to be both antigen and IL2-dependent in such microcultures. Furthermore, P815 stimulating cells could be replaced by 5 other H-2d cell lines of differing tissue origin. In limiting dilution studies, 1-2% of Lyt-2+ CTL-P (contaminated by less than 0.2% macrophages) could be induced to grow and express cytolytic activity in the presence of irradiated P815 and rIL2. Taken together, these data indicate that neither accessory cells nor differentiation factors (other than IL2) are absolutely required for alloantigen-induced growth and differentiation of CTL-P.