Experimental Research On Immunologic Tolerance Induced By Immature Dendritic Cells Treated With FK506 In Rat Allograft Transplantation

[Objective] To study the effect of immature dendritic cells (imDCs) treated withFK506 on immunologic tolerance in rat allograft organ transplantation and toinvestigate the mechanism of immunologic tolerance induced by imDCs.[Methods] Bone marrow cells of Wistar rats were cultured with low dose ofrecombinated rat GM-CSF(1.5ng·ml^-1) and IL-4(4 ng·ml^-1) and a large quantity ofimDCs treated with LPS and FK506 respectively were obtained, of which the degreeof maturity were identifid by morphology and FCM. The SD rats were divided intothree guoups: Group1——control group, in which normal sodium(1.0ml) wasinjected via vena caudalis seven days before the operations; Group 2——treatmentgroup without FK506, in which 2×10⁶(1.0ml) imDCs without treatment by FK506were injected via vena caudalis seven days before the operations; Group 3——treatment group with FK506, in which 2×10⁶(1.0ml) imDCs treated with FK506 wereinjected via vena caudalis seven days before the operations. Cervical hearttransplantations were performed in which Wister rats were used as donors and SD ratsas allograft recipients. Heart allograft survival was monitored and one-way MLR,heart pathology and the levels of IL-2,IL-4,IL-10,IFN-r in the serum weredetected.[Results] 1. The cells we obtained were verified to be imDCs: the expressions ofCD80 and CD86 were low in the separated cells analyzed by FCM, and theirexpressions were up-regulated obviously because of the stimulation of LPS. Theup-regulation of CD80 and CD86 could be restrained by FK506.2. 45 cases of cervical heart transplantation were performed in rats and theachievement ratio was 80.0 %. H test showed that there was high significantdifference of heart allograft survival in the three groups (P＜0.01); q test showed thatthe heart allograft survival of groupl was high-significantly different from that ofeither group2 or group3(P＜0.01), and also with statistical difference between the latter two groups(P＜0.05).3. As Wister rat spleen cells being the stimulating cells, the SI value ofgroup2(treatment group without FK506) was 3.48±0.84 and group3(treatment groupwith FK506) 3.59±0.68, both of which were significantly lower than 6.83±0.47 ofgroupl(control group) (P＜0.01), but no difference was observed between group2 andgroup3. As Lewis rat spleen cells being the stimulating cells, the SI value had nosignificant difference between treatment groups(group2:6.57±0.51, group3: 6.67±0.66)and control group(6.58±1.03) (P＞0.05).4. Analysis of variance showed that, there was high significant difference for serumconcentrations of IL-2,IFN-r,IL-4,IL-10 in the three groups(P＜0.01). S-N-K testshowed that the expression levels had no significant difference on 7th day for IL-2 andon 14th day for IFN-r between group2 and group3, but had high-significant differencebetween others(P＜0.01). The concentrations of IL-2 and IFN-r expressing on Th1were lower, and that of IL-4 and IL-10 expressing on Th2 were obviously higher ingroup2 and group3.5. The heart pathological examination showed congestion, swelling, quantities ofinflammatory cells infiltrating and degeneration and necrosis of the myocardial fibersin control group; the infiltrating cells decreased and the degeneration and necrosiswere not so obvious in treatment group without FK506; inflammation, degenerationand necrosis were scarcely seen in treatment group with FK506.[Conclusion] 1. FK506 can restrain DCs'maturity obviously.2. ImDCs can induce immunologic tolerance in rat heterotopic heart transplantationsuccessfully; ImDCs treated with FK506 can enhance the effect.3. The immunologic tolerance induced by imDCs is donor specific.4. ImDCs may induce the immunologic tolerance by means of modifying the immuneresponse type of T cells (immune deflection from Th1 to Th2), mediating thegeneration of regulatory T cells (T-reg) and inducing T cells disenabling.