Expression of interleukin-21, interleukin-21 receptor alpha and related type I cytokines by intravascular graft leukocytes during acute renal allograft rejection

Abstract: Interleukin-21 (IL-21), a member of the type I cytokine family, regulates central functions of immunity. Within this family, signaling is mediated via a receptor complex consisting of a high-affinity receptor chain and the common γ-chain (IL-2Rγ, CD132). We analyze the mRNA expression of IL-21, IL-21 receptor-α (IL-21Rα) and family members IL-15, IL-2Rγ, IL-21Rα, IL-15Rα, IL-2/15Rβ, as well as IL-2Rα (CD25) in leukocytes isolated by vascular perfusion of rat renal allografts. Mononuclear leukocytes expressed increased amounts of IL-21Rα mRNA and protein during acute rejection. Most IL-21Rα-positive cells were monocytes. Furthermore, IL-21 and IL-2Rα mRNA expression was strongly increased. No changes in IL-2Rγ, IL-2/15Rβ, IL-15, and IL-15Rα mRNA expression levels were seen. In conclusion, we demonstrate that IL-21Rα expression is induced in intravascular monocytes in vivo in response to allogeneic transplantation. The function of the IL-21/IL-21R system in monocytes and during acute allograft rejection remains to be established. [Copyright &y& Elsevier]