Effects of Glucocorticoids and Cyclosporine on IL-2 and IκBα mRNA Expression in Human Peripheral Blood Mononuclear Cells

To evaluate molecular mechanisms that might account for the heterogeneity in the in vitro responsiveness of individual subjects' peripheral blood mononuclear cells (PBMC) to immunosuppressive drugs, the authors quantitated in normal human cells the suppressive effects of the glucocorticoids prednisolone and methylprednisolone and of cyclosporine on interleukin‐2 (IL‐2) mRNA expression and IL‐2 production, as well as the stimulatory effect of these drugs on IκBα mRNA expression. As expected, cyclosporine was significantly more suppressive than either glucocorticoid of IL‐2 mRNA expression and IL‐2 production by mitogen‐stimulated PBMC, with variable degrees of inhibition in cells from individual subjects. The authors confirmed in human PBMC the stimulation of IκBα mRNA expression by the glucocorticoid reported by others in HeLa and transfected Jurkat cell lines. In addition, the authors observed a stimulatory effect on IκBα mRNA expression by cyclosporine as well in 8 of 10 PBMC preparations studied, suggesting a possible role of calcineurin in the regulation of IκBα a production. Interindividual variability in the intracellular mechanisms of action, possibly based on molecular polymorphisms, might be one factor contributing to differences among patients in their clinical responses to treatment with such drugs.