Generation of CFU-C/suppressor T cells in vitro: An experimental model for immune-mediated marrow failure

T cells were derived from the bone marrow of 8 healthy donors and fractionated, according to their receptors for the Fc fragment of IgG, into T(G)⁺ and T(G)^- lymphocytes. These were then cocultured with autologous or allogeneic bone marrow cells in agar in the CFU-C assay. No significant suppression of colony formation could be detected. Total T, T(G)⁺, and T(G)^- cells were then incubated for 18 hr with PWM, washed, and cocultured with bone marrow cells. PWM-treated T(G)^- cells showed no significant CFU-C suppressor activity, whereas PWM-treated total T and T(G)⁺ cells inhibited colony formation of both autologous and allogeneic marrow cells. The supernatant of PWM-treated total T and T(G)⁺ cells also inhibited colony formation. PWM alone enhanced colony formation. The results of this study indicate that normal T cells can be activated in vitro to become CFU-C/suppressor cells after PWM stimulation, and that this effect is mediated by T cells with the Fc receptor for IgG.