Cimetidine abrogates suppressor T cell function in vitro

Cimetidine increased the [3H] thymidine incorporation of normal human mononuclear cells in culture both when unstimulated or when under the stimulus of phytohemagglutinin or pokeweed mitogen (PWM). It also increased their supernatant immunoglobulin production under PWM stimulus. These effects were higher when the cells were preincubated with cimetidine than when it was added simultaneously. To determine if this effect of cimetidine reflects an abrogation of suppression we studied concanavalin-A-induced suppressor function of normal mononuclear cells using both [3H] thymidine incorporation and immunoglobulin synthesis as indicator systems and found that preincubation with cimetidine caused significant decrease in suppressor cell function in both systems.