RGMB and graft versus host disease: We hypothesized that if mAb 9D1 but not 2E11 was effective at preventing xenograft GvHD then RGMb blockade-mediated protection from xenograft GvHD is dependent on recipient mouse epithelium or antigen presenting cells, while if mAb 2E11 was effective at preventing xenograft GvHD, then RGMb blockade-mediated protection from xenograft GvHD is acting primarily through RGMb on donor mononuclear cells (human).