Met-RANTES, a chemokine receptor antagonist, is used to suppress acute rejection at early stage following small bowel allografting in rats

BACKGROUND: Rejection is the main cause of the failure in small bowel transplant. Chemotatic factor RANTES and receptor mediated cellular immunity are very important in acute rejection.OBJECTIVE: To explore the immunosuppressive effect of early adopting chemokine receptor antagonist, Met-RANTES after small bowel transplant on acute allograft rejection and its coordinative effect with Tacrolimus (FK506).DESIGN: Randomized complete-block design, controlled animal experiment.SETTING: Department of General Surgery, the 451 Hospital of Chinese PLA; Laboratory of Department of Gastrointestinal Surgery, Xijing Hospital, Fourth Military Medical University of Chinese PLA; Electronic Microscope Center, School of Basic Medicine, Fourth Military Medical University of Chinese PLA.MATERIALS: This study was carried out in the Laboratory of Department of Gastrointestinal Surgery, Xijing Hospital,Fourth Military Medical University of Chinese PLA from September 2003 to March 2005. Totally 192 animals including 96 SD rats (donors) and 96 Wistar rats (recipients) were involved in this study. Heterotopic segmental small bowel transplantation was performed.METHODS: The transplant rats were divided into 4 groups averagely by the randomized complete block design: control group (allogeneic small bowel transplant untreated group), Met-RANTES group(200 μg/d, 0-7 days, i.p.), FK506 group [0.5 mg/(kg·d) ,0-7 days,i.p.], Met-RANTES + FK506 group [Met-RANTES, 200 μg/d,0-7 days,i.p.+ FK506 0.5 mg/(kg ·d),0-7 days, i.p.]. Rats in the latter 3 groups were intraperitoneally administrated after transplant within 7 days successively.Rats in the control group were not given any treatments before and after transplant. Postoperatively, gross status,survival time and immunocyte infiltration were observed. Pathological examination was conducted in 6 rats of each group on postoperative days 3, 5 and 7. Fluorescent staining and successive quantitative measurement were conducted to detect the expressions of intragraft RANTES, CD4~+, CD8~+ and CD25~+ T lymphocyte. Survival duration of the rest 6 rats of each group was observed for 5 weeks.MAIN OUTCOME MEASURES: ① Survival time of rats in each group following transplant. ② Pathological changes of small bowel intragraft of rats in each group. ③ RANTES and T lymphocyte expressions of rats in each group.RESULTS: Following transplantation, 96 Wistar rats (recipient) were all involved in the final analysis. ①Compared with control group, the survival time of rats in Met-RANTES group, FK506 group, Met-RANTES + FK506 group was significantly longer (P ＜ 0.01). In addition, rats in Met-RANTES + FK506 group survived the longest. There were significant differences in survival rate as compared with Met-RANTES group and FK506 group (P ＜ 0.01). ②All rats in the control group died of acute rejection and infection. Histopathologic examination showed mild, moderate and severe rejection on the postoperative days 3,5 and 7, respectively. No obvious rejection was found in the rats in the Met-RANTES group, FK56 group and Met-RANTES+FK506 group on the postoperative days 3,5 and 7. ③Postoperatively, intragraft RANTES expression of rats was significantly higher in each time period in control group than in the other 3 groups (P ＜ 0.01), and its dynamic change was positively correlated with the process of acute rejection; The expression of intragraft RANTES, CD4~+, CD8~+ and CD25~+ T lymphocytes of rats was significantly lower, respectively, in the Met-RANTES group and Met-RANTES+FK56 group than in the control group (P ＜ 0.01).CONCLUSION: Met-RANTES may obviously suppress acute allograft rejection in small bowel transplant, effectively protect the function of grafts, and significantly prolong the survival time of the recipients. In addition, Met-RANTES may enhance the immunosuppressive function of small dose of FK506[0.5 mg/(kg · d)].