Glucocorticoids are reported to bias cytokines to a Th2 phenotype. However, this dogma has been advanced largely from studies utilizing potent glucocorticoid analogs. The current study was conducted to revisit the issue of glucocorticoid modulation of Th1/Th2 cytokine production and evaluate migration inhibitory factor (MIF) mRNA expression in cultured pig splenocytes treated with physiologically relevant concentrations of cortisol (CORT). Dexamethasone (DEX) was included for comparison. In Experiment 1, DEX, at 150 and 300 nM, suppressed concanavalin (ConA)-stimulated IFNγ at both 12 and 24 h in culture, and IL-10 at 24 h (P < 0.05). Both 150 and 300 nM CORT suppressed IL-10 at 24 h (P < 0.05), but neither concentration affected IFNγ at 24 h. In Experiment 2, cells were cultured with a broader range of CORT for 48 h following ConA. Parallel cultures with identical treatments also were conducted in separate plates for evaluation of glucocorticoid regulation of MIF mRNA. IFNγ was reduced by 300 nM DEX at 12, 24, and 48 h (P < 0.05), whereas 150 and 300 nM CORT blunted IFNγ at 24 h (P < 0.05), but not 48 h. ConA increased IL-2 (P < 0.01), but none of the steroid treatments affected IL-2. At both 12 and 24 h, IL-10 was reduced by 300 nM DEX and by 150 and 300 nM CORT (P < 0.05). ConA increased relative abundance of MIF mRNA (P < 0.001), but no steroid treatment affected MIF mRNA. In Experiment 3, steroid additions were delayed by 24 h after ConA, and cytokine concentrations evaluated 48 h later. Again, separate cultures were used for determination of effect of treatments on MIF mRNA. None of the steroid treatments affected IFNγ, but 300 nM DEX reduced IL-10 (P < 0.05). All of the CORT treatments (75-300 nM) reduced MIF mRNA (P < 0.05), whereas DEX did not affect MIF mRNA in this experiment. The current experiments suggest that both DEX and high physiological concentrations of CORT can suppress both type 1 and type 2-like cytokines in cultured pig splenocytes. But, IL-10 was generally more sensitive to CORT suppression with increased time in culture than was IFNγ. In addition, MIF mRNA could be suppressed by delayed addition of CORT to porcine splenocytes. Taken together, the data do not support the hypothesis that CORT directs the cytokine milieu toward a type 2 bias in cultured pig splenocytes. © 2002 Elsevier Science B.V. All rights reserved.
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