Effects of methylprednisolone on the in vitro generation of human secondary cytotoxic lymphocytes.

The effects of methylprednisolone on the induction of secondary proliferative and cytotoxic lymphocytes in human mixed lymphocyte cultures (MLCs) have been studied. Concentrations of methylprednisolone (MP) as low as 0.01 microgram/ml proved highly effective in inhibiting the generation of cytotoxic memory cells if the steroid was present during the first 5 days of the priming mixed lymphocyte culture. The generation of cytotoxic lymphocytes was also inhibited if the steroid was added along with the restimulating cells on day 10, although the degree of inhibition was not as great as that seen when steroids were added to the cultures at their initiation. Cultures containing 1 microgram of MP per ml during the priming phase required 10 times as many effector cells to achieve a comparable level of cytotoxicity compared to control cultures without steroids. Our results indicate that an important aspect of the immunosuppressive role of steroids is the prevention of the generation of specific memory cells following exposure to alloantigens.