| OBJECTIVES: To evaluate the effect of nuclear factor-kappa B (NF-κB) inhibitor pyrrolidine dithiocarbamate (PDTC) on the cell-surface expression of costimulatory molecules (CD80, CD86) of dendriteic cells (DC) and the discordant cardiac xenograft rejection by the model of heterotopic cardiac xenotransplantation from guinea pig to rats using modified Ono's procedure, and to explore the mechanisms of immuneosuppression of xenograft.METHODS: Cardiac xenograft from guinea pig was transplanted into the abdomen of SD rat. Hyperacute rejection was depleted by using Chinese Cobra Venom Factor (CVF). The recipients were divided into six groups. Group A (control group): without pretreatment. Group B (PDTC group): PDTC was injected into the abdominal cavity with a dose of 200 mg/Kg. Group C (transplantation group): Cardiac xenograft from guinea pig was transplanted into the abdomen of SD rat. Group D (PDTC+transplantation group): PDTC was injected into the abdominal cavity with a dose of 200 mg/Kg one hour before transplantation. Group E (CVF+transplantation group): the recipients were injected with CVF 40u/kg in abdomen and CVF 60u/kg were injected in vein again just before transplantation 24 hours later. Group F (PDTC+CVF+transplantation group): PDTC and CVF were injected before transplantation. Positive nuclear staining of NF-κB (p65 subunit) was taken to reflect NF-κB activation. To explorethe the tolerance mechanisms by performing mixed lymphocyte reaction (MLR) of rats of group A and group B. A spleen DC-enriched fraction was obtained based on differential adherence and low-density properties. The expression of OX-62, CD80 and CD86 of DC was detected by fluid cytometry (FCM). The grafted heart mean survival time (MST) and the pathology were observed.RESULTS: (1)The expression of OX-62 of the spleen DC-enriched fraction is15.04±13.15%.(2)The basic expression of p65 is 6.36%, which decreased after the injection of PDTC. The expression of p65 increased after transplantation: group C: 7.73%, group D: 6.13%, group E: 24.01%, group F: 10.26%. The expression of p65 of group A is lower than group E and group F (P<0.05), and group E is lower than group F (P<0.05). (3)The immune response of the rats of group B was weaker than that of group A proved by MLR assay. (4)CD80 is not expressed in any of the all groups. The basic expression of CD86 is 11.02±1.33%. And the expression didn't change after the injection of PDTC. The expression of CD86 increased after transplantation: group C: 33.14±1.11%, group D: 13.26±0.67%, group E: 54.10±2.07%, group F: 19.06±0.93%. The expression of CD86 of group E is higher than group C (P<0.05), while group C and group E is higher than group D and group F. (5)MST: Group C: 25.40±5.73min. Group D: 24.20±4.82min. There is no difference between these two groups (P>0.1). Group E: 320±27.39min, which is longer than group C and group D (P<0.05). Group F: 518±54.95min, which is longer than group E (P>0.05). (6)Pathology: The donor hearts in group C and group D showed hyperacute rejection (HAR) change. And acute vascular rejection(AVR)change took place in group C and D.Conclusion: The population of the spleen DC-enriched fraction we obtained is great enough to detect the cell surface molecules of dendriteic cells (DC). The increase of the expression of CD86 of DC of the recipients after transplantation was suppressed by injecting PDTC, which also prolonged the MST and suppress the AVR to a certain extent. And the reduction of the expression of CD86 may suppress the differentiation of Th2 cells and the generation of IgG.
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