OBJECTIVETo study the therapeutic effect of agonistic CD40 monoclonal antibody combined with tumor specific cytotoxic T lymphocyte (CTL) on B lymphoma.

METHODSHuman B lymphoma cell line, Daudi cells, were cultured with CD40 mAb (5C11) for 24 and 48 hours, respectively. Annexin V/PI-binding assay was employed to analyze apoptosis, and FCM to analyze Fas (CD95) expression. Human peripheral monocyte-derived DC were loaded with apoptotic Daudi cells and stimulated by SC11 for further maturation. Tumor specific CTL were generated in vitro by co-culture of mature DC with autologous T lymphocytes. DNA fragmentations of Daudi cells treated with 5C11, CTL or 5C11 combined with CTL were determined by JAM assay. To establish the B lymphoma model, Daudi cells were subcutaneously injected into humanized SCID mice (hu-SCID). 1 or 3 weeks after tumor transfer. tumor-bearing mice were respectively treated with SC11, CTL, 5C11 combined with CTL by intraperitoneal injection. Tumor volume in differently treated mice was measured every week after therapy, and the survival of tumor-bearing mice was recorded.

RESULTS5C11 significantly up-regulated FAS expression in Daudi cells, but had no significant effect on apoptosis rate of Daudi cells. Tumor-specific CTL could effectively kill Daudi cells. Fragmentation of Daudi cells co-cultured with CTL was remarkably enhanced by combination with SC11. Tumor growth in hu-SCID mice was apparently delayed by treatment with SC11, CTL, or SC11 combined with CTL. Moreover, minimal tumor burden mice got 30.0% or 70.0% complete remission (CR), respectively, when received CTL treatment or combination treatment of SC11 with CTL, and the lifespan of tumor bearing mice was also prolonged significantly.

CONCLUSIONSC11 may enhance the sensitivity of Daudi cells to apoptosis by up-regulation of Fas expression and promote cytotoxicity of CTL in vitro and therapeutic effect in vivo.