T-Cell-Directed Immunosuppression Allows Prolonged Survival of Xenogeneic Pig Islets in Monkeys

IN a previous study we demonstrated that porcine islets of Langerhans transplanted to monkeys will not be hyperacutely rejected. In immunosuppressed monkeys (cycplophosphamide, cyclosporine [CyA], and prednisolone) rejection occurred in the second week posttransplantation. Rejection infiltrates were dominated by T cells. We therefore wanted to investigate whether a more T-cell-directed immunosuppressive regimen could improve graft survival. Our aim was to deplete recipients of T cells prior to transplantation (using ATG) and prevent rejection posttransplantation using a combination of CyA, prednisolone, and anti-IL-2R antibody (Zenapax).