Improvement Of Transplantation Tolerance Of Skin Allograft By Infusion Of Donornkt Cells And Its Mechanism

Objective:The development of various combinations of immunosuppressive therapy has significantly improved the short-term graft survival rates. However, a constant proportion of organs were lost every year due to chronic allograft rejection and immunosuppressive drug toxicity. The induction of donor-specific tolerance has the potential of at least partially resolving this problem, since it might prevent chronic rejection and drug toxicity at the same time.An important mechanism that maintains allogenic antigen specific immune tolerance functions through suppressive regulatory T cells. As a kind of lymphocyte, natural killer cells (NKT cells) coexpress the TCR chain and NK markers and are restricted by MHC class I-like CD1d molecules. Recently, NKT cells are regarded as a kind of important cells to regulate immune responses, especially in induction and maintain of immune tolerance during transplantation of organ.Our Experiments investigate the impact of donor natural killer T cells (NKT) intravenous infusion on the survival period of the allograft, mixed lymphocyte reaction (MLR), delayed type hypersensitivity (DTH), some cytokines and adoptive transfer assay with murine skin transplantation model, at the same time compared with the traditional suppressive agent-CsA, so as to providing theoretical and experimental foundations of Astragalus for the therapy to allograft rejection andtolerance induction.Methods:1. Skin of C57BL/6 mice was transplanted to BALB/c mice. Control group: Sodium Chloride was given, group NKT: BALB/c mice were given an intravenous infusion of (5×10~6) donor NKT before transplantation and Sodium Chloride were give after transplantation, group CsA: Ciclosporin (CsA)(4mg/kg) were given after transplantation, group NKT+CsA: NKT were given before transplantation and CsA were given after transplantation. Survival conditions of grafted skin and general condition of mice were observed daily; 14 days after induction of tolerance the MLR and DTH of tolerance BALB/c mice were examined to confirm the tolerance status. Adoptive transfer assay and analysis of cytokine interleukin-10, interleukin-4 and interleukin-2 mRNA expression in tolerant mice were performed to further explore tolerance mechanisms. Results:2. Compared with group control, intravenous infusion of donor NKT cells before transplantation and NKT cells combined with CsA after transplantation apparently prolonged the survival time of the allograft.3. On the day 14 (the top period of the rejection), intravenous infusion of donor NKT cells before transplantation inhibited MLR, decreased specific memory response of T cells.4. Intravenous infusion of donor NKT cells before transplantation inhibited DTH evidently.5. Transplantation tolerance induced by donor NKT cells can be transferred adoptively.6. Intravenous infusions of donor NKT cells can up-regulate the level ofinterleukin-10 and interleukin-4 and down-regulate the level of interleukin-2. Conclusions:1. Intravenous infusion of donor NKT cells before transplantation can prolong thesurvival time of the allograft.2. Intravenous infusion of donor NKT cells before transplantation can inhibit DTH evidently.3. Transplantation tolerance induced by donor NKT cells can be transferred adoptively. 4. Intravenous infusions of donor NKT cells can up-regulate the level of interleukin-10 and interleukin-4 and down-regulate the level of interleukin-2.