A major conceptual advance is the formulation that type I cytokines (such as IL-2 and IFN-γ) enhance cellular immunity and are host-protective, and that type II cytokines (such as IL-4 and IL-10) dampen cellular immunity and facilitate the progression of infection. We have explored the intragraft expression of type I and type II cytokines during human renal allograft rejection. RNA was isolated from 98 allograft biopsies, and reverse transcription-PCR was used to amplify and identify intragraft expression of mRNA encoding IL-2, IFN-γ, IL-4, or IL-10. Intragraft expression of IL-7 mRNA and TGF-β1 mRNA was also investigated. Our investigation demonstrated that: (a) intragraft expression of IL-10 mRNA and IL-2 mRNA are significant correlates of acute rejection; (b) IL-4, IL-7, IFN-γ and TGF-β1 mRNA expression do not correlate with acute rejection; and (c) IL-10 does not prevent in vivo expression of IFN-γ, IL-2, IL-7, or TGF-β1. Our studies identify, for the first time, a significant association between intragraft IL-10 mRNA expression and acute rejection, and suggest that treatment strategies capable of constraining IL-10 expression might be of value in the prevention of acute rejection.
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