CD40 and vasculitis: Although xenograft function remained unchanged with small reductions in anti-CD40 MAb doses 1 yr after transplant (N = 2), complete cessation of anti-CD40 therapy led to rejection with characteristic features of TMA, vasculitis, intravascular thrombus, myocardial necrosis, epicardial hemorrhage, and a rapid rise of serum anti-pig antibodies (138).