TNF Enhances CD4+ T Cell Alloproliferation, IFN-γ Responses, and Intestinal Graft-Versus-Host Disease by IL-12-Independent Mechanisms

Abstract

Inhibition of TNF/TNFR2 interactions ameliorates intestinal graft-vs-host disease (GVHD) and Th1 cytokine responses induced by transfer of B6 CD4+ spleen cells into irradiated MHC class II disparate B6.C-H-2bm12 (bm12) × B6 F1 recipients. The present studies examined whether these effects of TNF are IL-12 dependent. T cell proliferative responses of B6.129S1-IL-12rb2tm1Jm (B6.IL-12R−/−) responder spleen cells were found to be comparable to those of control B6 spleen cells. TNF inhibition reduced T cell proliferation and IFN-γ production in supernatants of MLC using either B6.IL-12R−/− or control B6 responder cells. GVHD induced wasting disease in recipients of B6.IL-12R−/− CD4+ spleen cells that received a TNF inhibitor-encoding adenovirus (5.4 ± 6.5% weight loss (n = 7)) was significantly reduced compared with levels of weight loss observed in recipients that had received a control adenovirus (25.7 ± 12.2% weight loss (n = 11), p = 0.001). Furthermore, TNF inhibition was associated with a reduction in colonic GVHD scores (p = 0.039) and in the percentage of the splenic CD4+ T cells that expressed IFN-γ (16 vs 6%). These findings indicate that TNF promotes CD4+ T cell alloproliferation, IFN-γ responses, and intestinal GVHD by IL-12-independent mechanisms.