Renal transplantation following IUHCT. Chimerism profile of renal allograft recipients, with arrows marking the time of transplantation (A). Evaluation of the kidney allograft in tolerant animals at 6 months reveals no evidence of rejection on H&E (B) or PAS (C). In the nonchimeric control dog, there is evidence of acute rejection with significant and severe lymphocytic infiltrate, inflammation, and tubulitis on H&E (D) and PAS (E) upon transplant nephrectomy 5 days following transplantation. This animal manifested an early and acute Systemic Inflammatory Response Syndrome reaction characterized by fevers, anorexia, and weight loss, consistent with acute rejection observed histologically and requiring urgent explant, upon which all symptoms resolved. In this animal, gross examination of the kidney revealed a markedly shrunken and discolored appearance. In the animal with the lowest chimerism levels (3% to 7%), there was persistent lymphocytic infiltrate on both H&E (F) and PAS (G) at 6 months, consistent with Banff class 3 subclinical chronic rejection; no clinical sequelae were noted, and the animal remained healthy throughout the planned 6-month observation. Upon gross examination, this allograft had a normal appearance. All images ×20.