In these mice we compared the ability of anti-PD-1 and anti-CTLA-4 mAbs as single agents, in combination, and MEDI8500 to break tolerance to the mouse environment, using the development of GvHD lesions as a surrogate to evaluate aggravated antigenic T cell response and as an endpoint to determine relative potency. Here, CTLA4 is linked to graft versus host disease.