Regulation of human suppressor cell function by thymosin.

Suppressor cells were induced in vitro by Con. A using human peripheral blood lymphocytes. Suppressor cell function was evaluated by mitogen stimulation (PHA and Con. A) and in mixed lymphocyte culture (MLC), Thymosin fraction V was able to block the effector phase more significantly than the induction phase of suppressor cell expression. This effect was additive if thymosin fraction V was present both during the induction and effector phases.