Abstract： Objective To study the correlation of HLA-G levels with acute rejection and CMV active infection post-kidney transplantation.Methods A total of 132 initial kidney transplantation recipients were divided into kidney function stable group (F),acute rejection group (AR),CMV group according to whether they had active CMV infection and acute rejection.Forty-one healthy donors served as control group (H).HLA-G levels and mRNA expression were analyzed by using flow cytometry,ELISA,RT-PCR and Western blotting.Immunohistochemical staining was used to detect the HLA-G expression in kidney biopsies.Results The expression levels of mHLA-G1 were low in all 4 groups pre-transplantation.Only CMV group had significantly more CD14+ mHLA-G1+ cells post-transplantation (P＜0.05).sHLA-G5 levels were higher in F group than in H group (P＜0.05),but there was no significant difference among other groups pre-transplantation (P＞0.05).sHLA-G5 levels were increased significantly in CMV group as compared with F group (P＜0.05),and those in F group were higher than in H and AR groups (P＜0.05).Renal tissue biopsies from 21 renal transplantation recipients with AR indicated that HLA-G5 was expressed negatively in 17 patients,positively in 3 patients and 1 weakly positively.HLA-G was positive in the kidney tissue of 9 patients out of 9 patients with active CMV infection.In total 132 recipients,AR incidence was significantly lower in CMV ( + ) group (7.1 ％,2/28) than that in CMV ( - ) group (24.0 ％,25/104).Conclusion The sHLA-G5 may contribute to predict AR and CMV active infection; AR and CMV active infection may be correlation with immune balance in kidney transplantation recipients.