To investigate the imbalance state of helper T lymphocytes(Th)and cytotoxic T lympho- cytes(Tc)and the roles of Th1/Th2/Th3 and Tc1/Tc2 cells in renal transplantation rejection,the per- centages of these cells in peripheral blood of 24 cases of renal transplantation recipients with acute re- jection and the dynamic changes of the CD4/CD8 ratio were determined by flow cytometry analysis, while 30 cases of healthy individuals were set up as controls.In these healthy controls,the percentages of the Th1,Th2 and Th3 cells were(10.45±8.15)%,(5.05±4.15)%and(3.90±3.21)%, and those of Tc1 and Tc2 cells were(9.83±7.03)% and(4.51±2.17)%,respectively.However, the percentages of Th1 and Tcl cells in peripheral blood of the stable recipients after transplantation were(7.29±5.62)%and(7.04±5.15)%,showing definite reduction,while those of Th2,Th3 and Tc2 cells showed significant increase,(6.34±5.67)%,(4.94±4.14)% and(6.86±4.42)%,respectively.In case of recipients with acute rejection,the percentages of Th1 and Tc1 cells appeared to be(18.55±13.21)% and(15.84±11.72)%,also showing significant increase,but those of Th2,Th3 and Tc2 cells appeared to be reduced,(4.19±3.62)%,(3.02±2.83)% and (3.88±1.63)%,respectively.Significant differences could be detected among these three groups(P<0.05).The CD4/CD8 ratio in cases with acute rejection was higher than those of stable recipients (2.24±0.59 vs 1.95±0.45),but that of the stable recipients and healthy controls(1.98±0.31) showed no any significant difference.From the above observation,it is evident that imbalance between Th1,Th2 and Th3 with Tc1 and Tc2 cells may exist after renal transplantation and probably,the im- mune imbalance may be induced through the secretion of cytokines INF-γby Th1 or Tc1 cells,Ⅱ-4 by Th2 and Tc2 cells and TGF-βby Th3. To investigate the imbalance state of helper T lymphocytes (Th) and cytotoxic T lympho-cytes (Tc) and the roles of Th1 / Th2 / Th3 and Tc1 / Tc2 cells in renal transplantation rejection, the per centages of these cells in peripheral blood of 24 cases of renal transplant recipients with acute re- jection and the dynamic changes of the CD4 / CD8 ratio were determined by flow cytometry analysis, while 30 cases of healthy individuals were set up as controls. In these healthy controls, the percentages of the Th1, Th2 and Th3 cells were (10.45 ± 8.15)%, (5.05 ± 4.15)% and (3.90 ± 3.21)%, and those of Tc1 and Tc2 cells were (9.83 ± 7.03)% and respectively. However, the percentages of Th1 and Tcl cells in peripheral blood of the stable recipients after transplantation were (7.29 ± 5.62)% and (7.04 ± 5.15)%, showing definite reduction, while those of Th2, Th3 and Tc2 cells showed significant increase, (6.34 ± 5.67)%, (4.94 ± 4.14)% and (6.86 ± 4.42)%, respectively.In case of recipients with acute rejection, the perc (4.19 ± 3.62)%, ((4.19 ± 3.62)%, (3), (3), Tc1 cells and Tc1 cells were also found to be reduced to (18.55 ± 13.21)% and 3.02 ± 2.83)% and (3.88 ± 1.63)%, respectively.Significant differences could be detected among these three groups (P <0.05). The CD4 / CD8 ratio in cases with acute rejection was higher than those of stable recipients (2.24 ± 0.59 vs 1.95 ± 0.45), but that of the stable recipients and healthy controls (1.98 ± 0.31) showed no significant difference. From the above observation, it is evident that imbalance between Th1, Th2 and Th3 with Tc1 and Tc2 cells may exist after renal transplantation and probably, the im-mune imbalance may be induced by the secretion of cytokines INF-γby Th1 or Tc1 cells, Ⅱ-4 by Th2 and Tc2 cells and TGF-βby Th3.