Enhanced expression of the decoy receptor IL-13Ralpha2 in macrophages of Schistosoma japonicum-infected mice.

BACKGROUND: Type 2 cytokine interleukin (IL)-13 and its decoy receptor, IL-13 receptor (R) alpha2 appear to play a major role in tissue fibrosis of schistosomiasis and asthma. IL-13 is a key regulator of the extracellular matrix (ECM). It is known to signal to cells by binding to the IL-13Ralpha1, which then heterodimerizes with IL-4Ralpha. In contrast, IL-13Ralpha2 binds IL-13 with high affinity but does not signal. IL-13Ralpha2 is known to down-regulate granulomatous inflammation and prolong host survival in Schistosoma mansoni (S. mansoni) infection, but little is known about the location and expression level of IL-13Ralpha2 in the context of S. japonicum infection.

METHODS: We established S. japonicum-infected mouse models. Kinetic serum levels of IL-13Ralpha2 were examined with ELISA. IL-13Ralpha2 mRNA and protein of liver tissues were determined by PCR and immunoblotting analysis, respectively. Detection of IL-13Ralpha2 expression and location in macrophages was performed by TaqMan PCR and fluorescent immunocytochemistry technique, respectively.

RESULTS: A marked elevation of mRNA and protein expression of IL-13Ralpha2 was observed in mice during S. japonicum infection. An enhanced expression of IL-13Ralpha2 was further demonstrated in primary macrophages of murine schistosomiasis.

CONCLUSIONS: IL-13Ralpha2 in macrophages may be a critical contributor to pathogenesis of schistosomiasis. The data highlight the potential importance of cell signaling and antifibrotic gene therapeutics in T helper 2 cell (Th2)-mediated diseases.