NKR-P1+TCR????+ T (NKT) CELLS WERE INCREASED IN RAT HEPATIC ALLOGRAFT OF NATURAL ACCEPTOR AND REJECTOR

Abstract

183 NKR-P1+TCRαβ+T (NKT) cells are mainly distributed at the sites such as bone marrow and liver. NKT cells play an important role in the development and regulation of immune responses. We analyzed the immunological characteristics of NKT cells in rat liver transplantation. Methods; In acutely rejected combination, LEW (RT11) rats rejected DA(RT1a) liver grafts within 11 days (REJ; n=5). In natural tolerant combination, LEW rats indefinitely accepted BN(RT1n) liver grafts, (TOL; MST>100 days, n=5). Also in this combination, 10 Gy irradiated BN rats were used for donors to deplete donor passenger leukocytes and 4 days after irradiation. BN livers were transplanted in the LEW recipients (IRR). Intragraft mononuclear cells (IGCs) were collected on day 7 and 10 after transplantation for flow cytometry with anti-NKR-P1(3.2.3), anti-TCRαβ(R73) and anti CD4/CD8 mAbs, and spleen T cells were suspended for MLR. Total RNA was extracted from liver allografts and RT-PCR was done to analyze cytokine gene expression in the grafts. Serum cytokines were measured by ELISA assay. Results;Flow cytometry; In phenotypic analysis of IGCs on day 7 after transplantation, populations of T cells and NKT cells were significantly higher in REJ than in TOL. The ratio of NKT/TCRαβ+T cells was significantly (p<0.05) lower in REJ than in TOL (Table). Donor type NKT cells remained in the graft with the ratio (donor NKT/recipient NKT) of 6.7±0.8% in TOL, and 3.9±0.5% in REJ on day 7. MLR; Spleen T cells obtained from TOL on day 7 after transplantation displayed to be less responsive (41146.4±4170.8 cpm) against donor antigens than those from naive LEW rats (101300.2±4979.2 cpm). RT-PCR; Th1 cytokines (IFN-γ) were strongly expressed in the REJ grafts. Th2 cytoknes (IL-4 and IL-10) were expressed both in the TOL and REJ grafts. Serum IL-4 and IFN-γ were higher in TOL (5.75pg/ml and 12.07pg/ml) than in REJ (1.65pg/ml and 4.52pg/ml) on day 7. By donor irradiation, liver mononuclear cells were depleted from 3.0×107 to 6.0×105 /liver, and the grafts were rejected in the MST of 24.3±3.8 days. And the ratio of NKT/αβT cells was lower than that of the TOL. Conclusions; Donor derived NKT cells may be responsible for the induction of tolerance by a deviation of Th2 reactivity.Table