Reciprocal Expression of Enteric Antimicrobial Proteins in Intestinal Graft-Versus-Host Disease

We recently demonstrated that expression of alpha-defensins, the major antimicrobial peptides produced by Paneth cells, was severely suppressed in mice with graft-versus-host disease (GVHD). In this study, we found that antibacterial lectin, regenerating islet-derived III gamma (RegIII gamma) was upregulated in villous enterocytes, thus demonstrating the reciprocal control of enteric antimicrobial proteins in GVHD. Upregulation of RegIII gamma was mediated by a mechanism independent upon radiation-induced intestinal tract damage. MyD88-mediated signaling in intestinal epithelium was required for RegIII gamma upregulation in GVHD and antibiotic therapy downregulated RegIII gamma expression. These results suggest that MyD88-mediated sensing of the intestinal microbes disregulated in GVHD induces RegIII gamma upregulation in GVHD and argue a role for RegIII gamma in the pathogenesis of GVHD. (C) 2013 American Society for Blood and Marrow Transplantation.