In vivo and in vitro effects of methylprednisolone on human lymphocyte proliferation.

Lymphocytes obtained from normal volunteers 4 hr after intravenous methylprednisolone (1 mg/kg of body weight) were significantly less stimulated in vitro by several concentrations of phytohemagglutinin and concanavalin A. This effect was not due to diurnal variations. Significant decreases in the levels of circulating T lymphocytes (p < 0.001) at this time suggested cellular redistribution as a factor in decreased mitogen responsiveness. However, incubation of plasma, obtained 1 hr after methylprednisolone injection, with normal autologous lymphocytes suppressed the in vitro responses as well, indicating an additional direct corticosteroid effect on the lymphocytes.