A previous study in this laboratory demonstrated that a single dose of EtOH causes thymic atrophy and that elevated levels of endogenous glucocorticoids are responsible, at least in part, for this effect. In the present study using the same animal model, the effect of EtOH on the T-dependent antibody response to sheep red blood cells (SRBC) was evaluated. In addition, the effects of EtOH on the SRBC-induced expression of selected cytokines known to enhance or regulate humoral responses were evaluated. Administration of EtOH at 5.0 to 7.0 g/kg to B6C3F1 mice significantly and dose-responsively inhibited the generation of antibody-forming cells (AFC) after immunization in vivo or in vitro in Mishell-Dutton cultures. In contrast, direct addition of EtOH or its major metabolites to Mishell-Dutton cultures did not decrease the AFC response. In vivo administration of EtOH caused substantial decreases in the SRBC-induced expression of interleukin (IL)-1-beta, IL-2 and IL-4 mRNA in the spleen, as indicated by reverse transcription-polymerase chain reaction. The suppressed AFC responses and suppressed cytokine gene expression were prevented by RU 486, a potent glucocorticoid antagonist. Thus, suppression of cytokine gene expression by elevated levels of endogenous glucocorticoids may play a role in EtOH-induced suppression of the primary humoral response to SRBC. However, differences in dose-response patterns for suppression of cytokine gene expression and suppression of the AFC response suggest the involvement of additional factors.