Presently,one of the most potent immunotherapies is the application of bacillus Calmette Guerin(BCG)to prevent recurrences of the superficial bladder cancer.Despite its successful use,nonresponders and certain side effects remain a major obstacle.Therefore,current studies aim at developing recombinant BCG(rBCG)strains secreting Th1like cytokines to improve the effectiveness of the therapy.In this study,a new type of rBCG strain constructed by Tianjin institute of Urology was tested for its immunostimulatory capacity in vitro.Peripheral blood monocytes(PBMC)were stimulated by recombinant BCG and transformed into bacilli Calmette-Guerin activated killer(BAK)cells,and the effect of anticancer BAK cells was studied.Recombinant IFN-α-2b-BCG,wild-type BCG(wBCG),wild-type BCG and IFN-α-2b were coincubated with PBMCs respectively in vitro,and the proliferation of PBMC was detected with MTT in different time.BAK cells have the ability to kill bladder tumor cells,and the antitumor activity of effecter cells was determined by LDH release assay.The result of MTT showed that the proliferation of PBMC in the recombinant BCG group was more powerful than in the other two groups(P＜0.05).The result of LDH release assay showed that the antitumor activity of BAK cells stimulated by Recombinant BCG was the highest in all groups.We conclude that the recombinant BCG can activate more PBMCs to anti-bladder cancer in vitro than wild-type BCG does.