Induction kinetics of human suppressor cells in the mixed lymphocyte reaction and influence of prednisolone on their genesis

The induction kinetics of human suppressor cells in mixed lymphocyte cultures (MLC) and the influence of prednisolone on the genesis of these suppressor cells is reported. We induced over 1 to 6 days suppressor cells in one-way MLC (MLC-1), the inhibitory activity of which was tested on a secondary MLC (MLC-2), and on responder cells alone, where lymphocytes were obtained from the same lymphocyte donors as for the MLC-1. In four experiments the degree of inhibition ($\text{x}\text{?}\text{±}\text{SE}$) when suppressor cells were induced for 2, 4, or 6 days was 38.5 ± 11.8, 79.5 ± 7, and 85 ± 6%, respectively, compared to 50.5 ± 9.4, 83.3 ± 7.8, and 85.3 ± 9.8% when 500 ng/ml prednisolone was added to the MLC-1. A similar inhibition pattern was observed when the generated suppressor cells were incubated with responder cells only. The inhibitory activity of these MLC-induced suppressor cells was abrogated by irradiation with 3000 R. Suppressor cells apparently are generated in MLCs between Days 1 and 4; furthermore, their genesis is not affected by usual therapeutic concentrations of prednisolone.