TH2 CYTOKINE PROFILE MODULATION BY INTERLEUKIN-10 ADMINISTRATION AUGMENTS GRAFT ARTERIAL DISEASE IN MURINE HEART ALLOGRAFTS.

Abstract

977 Purpose: Th2 cytokines exhibit immunosuppressive properties on mononuclear cells in vitro, and recent studies suggest an association of Th2 cytokine induction with prolongation of allograft survival in animal transplant models. However, it is controversial whether treatment with Th2 cytokines suppresses alloresponses in vivo. In this study, we investigated the effects of systemic administration of interleukin (IL)-10 or anti-IL-10 on the severity of parenchymal rejection and graft arterial disease (GAD). Methods: Using a murine heterotopic cardiac allograft model, we transplanted across an MHC II disparity with C-H-2bm12 KhEg donors and C57BL/6 recipients. Recipients were either wild-type (WT) or interferon-γ deficient (GKO); we have previously demonstrated that interferon-γ deficiency leads to an abrogation of the development of GAD (Nagano, et al., 1997. J. Clin. Invest. 100: 550 ), and sought to investigate the role of IL-10 on this effect. WT recipients were treated with daily subcutaneous injections of recombinant mouse IL-10 (0.5, 1.0, or 2.5 μg/day; n=6/each group) or saline (n=4). GKO recipients were treated with intraperitoneal injection of anti-IL-10 neutralizing antibody (2 mg initially and 1 mg/week after transplantation; n=5) or the same volume of saline (n=4). Allografts were harvested at 8 weeks post-transplant and were evaluated by routine histology, immunohistochemistry (for co-stimulator and adhesion molecule expression), and flow cytometry to identify infiltrating cell populations and the cytokines being produced by those cells. Results: Systemic IL-10 administration induced Th2 cytokine production with significant synthesis of IL-4 and IL-10 in infiltrating lymphocytes in IL-10 treated recipients; both cytokines were undetectable in allografts from saline-treated WT recipients. However, despite the deviation to a Th2-type response, histological examination at 8 weeks demonstrated dose-dependent exacerbation of parenchymal rejection and GAD in allografts from IL-10-treated recipients, relative to grafts in saline-treated controls. Immunohistochemical analysis also showed a dose-dependent increase of CD8+ T cell populations and enhanced expression of B7-1 co-stimulatory molecule in the allografts of IL-10-treated WT groups. In GKO recipients, treatment with anti-IL-10 did not increase GAD, although there was increased expression of MHC II, ICAM-1, VCAM-1, B7-1, and B7-2 molecules on graft infiltrating cells, compared to saline-treated GKO recipients. Conclusions: The results suggest that although IL-10 has an anti-inflammatory effect in vitro, it augments both parenchymal rejection and GAD when administered in vivo, even in the setting of a shift to Th2-like cytokines. Moreover, the lack of GAD seen in grafts transplanted into GKO hosts cannot be attributed to effects mediated via IL-10.