Ischemia and consecutive reperfusion injury of the graft cannot be avoided in organ transplantation. One principal characteristic of this process is the temporary and permanent adherence of leukocytes to endothelial cells of the graft as well as damage of the associated tissue. Polyclonal antithymocyte globulins (ATGs) are used to prevent acute rejection after transplantation and to overcome graft vs. host disease. ATGs induce apoptosis and complement-mediated cell death in peripheral T-lymphocytes having the potential to inhibit leukocyte adhesion by direct binding to adhesion molecules. The aim of the present study was to analyse in a non-human primate model (cynomolgus monkeys) morphological changes within the microvasculature and the different cell-subpopulations upon ischemia/reperfusion after immunosuppressive treatment. Our results show a decrease of the tissue damage and WBC infiltration in muscular structures as well as a lower number of mononuclear cells in peripheral blood in the ATG-treated group compared to a non-treated control group. We may conclude that pATGs have a beneficial effect on the early mechanisms of ischemia/reperfusion injury.