The effect of IFN-gamma and alpha on Con-A stimulated T-cell proliferation: role of monocytes.

Interferon gamma (IFN-gamma) and alpha (IFN-alpha) have been shown to influence T-cell proliferation in several systems. Since both species of IFN affect monocyte (Mo) functions, it is conceivable that these effects are mediated through Mo. In the present study, the effect of IFN-gamma and alpha on concanavalin A (Con A)-driven T-cell proliferation was investigated under suboptimal culture conditions. T-cell proliferation was augmented by IFN-gamma. The stimulatory effect of IFN-gamma was Mo mediated and required the pretreatment of Mo with IFN-gamma prior to co-culture with T-cells. Addition of IFN-gamma during co-culture or pretreatment of T-cells with IFN-gamma was ineffective in achieving augmentation. IFN-gamma induced enhanced T-cell proliferation was not due to increased interleukin-I (IL-I) production by Mo pretreated with IFN-gamma, because addition of IL-I to control Mo-T-cells co-culture failed to increase T-cell proliferation. In contrast, IFN-alpha suppressed T-cell proliferation. The inhibitory effect of IFN-alpha was not mediated through Mo and could be achieved by preincubating the T-cells with IFN-alpha. These results demonstrate opposing effects of the two species of IFN on Con A-driven T-cell proliferation. In addition, Mo play an obligatory role in IFN-gamma induced stimulation, whereas Mo-IFN-alpha interaction is not required for IFN-alpha mediated suppression of T-cell proliferation.