Renal allograft rejection is prevented by adoptive transfer of anergic T cells in nonhuman primates.

Anergic T cells generated ex vivo are reported to have immunosuppressive effects in vitro and in vivo. Here, we tested this concept in nonhuman primates. Alloreactive T cells were rendered anergic ex vivo by coculture with donor alloantigen in the presence of anti-CD80/CD86 mAbs before adoptive transfer via renal allograft to rhesus monkey recipients. The recipients were briefly treated with cyclophosphamide and cyclosporine A during the preparation of the anergic cells. Thirteen days after renal transplantation, the anergic T cells were transferred to the recipient, after which no further immunosuppressive agents were administered. Rejection-free survival was prolonged in all treated recipients, and 3 of 6 animals survived long term (410-880 days at study's end). In the long-surviving recipients, proliferative responses against alloantigen were inhibited in a donor-specific manner, and donor-type, but not third-party, skin allografts were also accepted, which demonstrated that antigen-specific tolerance had been induced. We conclude that anergic T cells generated ex vivo by blocking CD28/B7 costimulation can suppress renal allograft rejection after adoptive transfer in nonhuman primates. This strategy may be applicable to the design of safe clinical trials in humans.

Modification of the leukapheresis procedure for use in rhesus monkeys (Macaca mulata).

One of the most serious problems in applying leukapheresis to human infants is the large extracorporeal blood volume (ECV), resulting in substantial loss of platelets and red blood cells (RBCs). In this study, we developed a safe and effective modified procedure to collect peripheral blood stem cells (PBSCs) from rhesus monkeys (Macaca mulata) using a Baxter CS3000+ Blood Cell Separator (Baxter, Deerfield, IL) with several devices that reduced chamber size and shortened the standard apheresis kit to decrease ECV from 130 to 70 ml. Pump speed was controlled by monitoring hematocrit values and platelet counts during leukapheresis. This system makes it possible to perform safe and effective leukapheresis in rhesus monkeys whose body weight is similar to that of human infants. A total of 12 leukapheresis procedures were performed in nine monkeys and resulted in the collection of sufficient numbers of white blood cells (mean, 1.38 x 10(9) cells/kg), CD34(+) cells (mean, 17.80 x 10(6) cells/kg), mononuclear cells (mean, 3.67 x 10(8) cells/kg), and colony forming units (mean, 75.02 x 10(6) cells/kg) in all cases. In addition, no complications, such as anemia or thrombocytopenia, occurred after leukapheresis. This modified leukapheresis procedure will be useful to test new approaches in gene therapy, perform organ transplantation using nonhuman primates, and collect PBSCs from human infants in a noninvasive manner. Our nonhuman primate model provides an important framework for such future clinical studies.