Pancreas allograft defined as absent or insignificant inflammation not involving ducts, veins, arteries, or acini. There is no graft sclerosis. The fibrous component is limited to normal septa and its amount is proportional to the size of the enclosed structures. The main targets of acute T-cell mediated allograft rejection (ACMR) in the pancreas are the acini, ducts, veins, and arteries. Arterial inflammation defines moderate and severe ACMR. Routine evaluation of C4d staining is necessary for an accurate diagnosis of ACMR versus antibody-mediated allograft rejection (AMR). AMR is characterized by injury to the vasculature due to deposition of antibodies in association with activation of the complement cascade.