In the mouse aortic allograft transplant model, the role of the uPA/ uPAR complex and the mammalian PAI-1 serpin in Serp-1-mediated reductions in vasculitis were analyzed using donor-transplanted aortic segments from mouse models that were deficient in uPAR or PAI-1 knock out mice. Here, SERP1 is linked to vasculitis.