Pancreas transplant pathology. A morphologic, immunohistochemical, and electron microscopic comparison of allogeneic grafts with rejection, syngeneic grafts, and chronic pancreatitis.

In an effort to establish diagnostic criteria for rejection and recurrent disease in transplanted pancreas, a comparative study was performed based on clinical diagnosis. Clinical rejection was diagnosed in patients who had decreased urinary amylase or increased blood glucose; they were treated for rejection and improved. A clinical diagnosis of recurrent diabetes was made in syngeneic transplant recipients with islet dysfunction. In addition, two control groups were used--nontransplant, nondiabetic pancreatitis patients and pretransplant normal biopsies from patients in the study. Morphologically, tissues were assessed for acinar inflammation, ductal changes, islet and nerve inflammation, and vascular changes. Immunohistochemical staining for insulin and glucagon was also performed to quantitate differences between the groups. Vascular changes (endothelialitis, vasculitis, obliterative endarteritis) were specific for rejection. Also, rejection was characterized by a lymphocytic or mixed infiltrate that involved the ducts. Recurrent diabetes was characterized by selective loss of beta cells with isletitis. Leukocyte common antigen and UCHL1 staining was helpful in identifying islet inflammation. An insulin/glucagon ratio of less than 1.0 appears to be specific for recurrent disease and in the absence of isletitis is a reasonable method for detecting recurrent disease at an early stage.