The effect of glucocorticoids on lymphokine production by T lymphocytes was examined by using long-term alloreactive T cell clones that secreted one or more of the lymphokines interleukin 2 (IL 2), interferon-gamma, macrophage-activating factor (MAF), and colony-stimulating factor when stimulated by an antigen or a mitogen. Production of all of these four lymphokines was inhibited when glucocorticoids were added at physiologic concentrations (10(-8) to 10(-6) M) to clones stimulated with concanavalin A (Con A). Clones were heterogeneous with respect to their sensitivity to glucocorticoid inhibition of MAF production; cytolytic clones were generally more resistant than noncytolytic clones. The glucocorticoid dexamethasone (Dex) and an IL 2-containing supernatant exerted opposing effects on clonal MAF production. Kinetics experiments showed that Dex inhibited MAF production by reducing the rate of secretion without causing a compensatory increase in the duration of secretion, whereas the IL 2 source increased the rate and the total amount of MAF secretion. Dex abrogated the effect of IL 2. Inhibition by Dex was apparent from the earliest time of detectable MAF production (about 4 hr after stimulation) and increased with longer exposure until production ceased (12 to 24 hr). Pre-exposure and removal of Dex before Con A stimulation also inhibited MAF release. Effects of Dex on lymphokine secretion by clones could be dissociated from effects on their growth in response to stimulator cells and IL 2. Factor production by the 16 clones tested was inhibited to some degree. Proliferation, however, by two of these clones (both cytolytic) was unaffected by Dex, whereas proliferation of two noncytolytic clones was strongly inhibited even in the presence of a saturating dose of IL 2.

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