Quantitative comparison of rapamycin and cyclosporine effects on cytokine gene expression studied by reverse transcriptase-competitive polymerase chain reaction.

We developed and applied a quantitative competitive polymerase chain reaction method to study the expression of various cytokine genes in Con A-stimulated murine splenocytes. This method relies on the use of competitive templates that differ from the target cytokine cDNA templates only by the introduction of a unique restriction endonuclease site in the center of each competitive template. After same-tube amplification using a single pair of oligonucleotide primers for both the target and competitive templates, restriction with the unique endonuclease yields 2 species that are readily resolved on agarose gel electrophoresis: full-length target and half-length competitor fragments. Using this method, we studied the time course and effects of CsA and rapamycin on IL-2, IFN-gamma, IL-4, and IL-10 gene expression following Con A stimulation. IL-2, IFN-gamma, and IL-10 share a common pattern of gene expression peaking at approximately 6 hr, while IL-4 gene expression peaks later, at approximately 20 hr. CsA very effectively inhibits expression of IL-2, IFN-gamma, and IL-4, but it inhibits IL-10 expression only 65%. Rapamycin inhibits IL-10 gene expression 100% and is less effective inhibiting the other cytokines. This pattern of inhibition is consistent with a calcium and protein kinase C independent pathway for IL-10 gene regulation and supports the notion that CsA and rapamycin may be used together to advantage.