Mobilization Of Dendritic Cell Precursors In Vivo By Administration Of P.acnes And The Study On DC-based Stomach Cancer Therapy

Objective: To mobilize DC precursors into circulation by P.acnes injection which resulted in inflammatory reaction in mice and to visit the possible mechanism. Then study the role of those DCs in Gastric Carcinoma Therapy.Methods: (1) C57BL/6J (B6) pure breed mouse were randomly assigned to two groups. The experiment group were injected with P.acnes via the tail vein, while the control group were injected with PBS. Peripheral blood was obtained at the indicated time intervals after P.acnes or PBS injection. Peripheral blood mononuclear cells (PBMNC) were prepared from peripheral blood. F4/80-B220-CD11c+ cells were then sorted from PBMNC by FACS. Then compare the quantitive difference of F4/80-B220-CD11c+ cells between two groups. (2)Freshly isolated F4/80-B220-CD11c+ cells were analysed by morphological observation phenotype analysis and mixed lymphocyte reaction (MLR). After cultured with cytokines, the same analysis were taken to confirm whether these cells could differentiate into mature DCs. (3)DCs mobilized by P.acnes injection were loaded with gastric carcinoma antigen by co-cultured with stomach cancer cell lysates. Then the kill effect of T cells stimulated with those DCs to stomach cancer cell was evaluated.Results: F4/80-B220-CD11c+ cells increased in circulation 1 hour after P.acnes injection and gradually reached a peak level 24 hour after injection. Freshly isolated F4/80-B220-CD11c+ cells did not exhibit the character of mature DCs. The major chemokine receptors they expressed are CCRl and CCR5 but did not express CCR7. After cultured with cytokines GM-CSF , IL-4 and TNFa, F4/80-B220-CD11c+ cellswere morphologically and phenotypically identical to typical DCs. The chemokine receptors they expressed CCRl and CCR5 were obviously down-regulated, but major expressed CCR7. The kill rate to stomach cancer cell of T cells stimulated with stomach-cancer-antigen-pulsed DCs mobilized by P.acnes injection was obviously high of T cells stimulated with unpulsed DCs. These activated T cells did not exhibit significant effect on melanoma cells.Conclusion: (1)P.acnes injection leads to rapidly mobilization of F4/80-B220-CD11c+ cells into circulation and these cells can differentiate into mature DCs in vitro. (2)The mechanism of DCs recruiment by P.acnes injection may be mediated by the interaction of chemokine receptors: CCR1, CCR5 and their corresponding chemokines. (3)DCs mobilized by P.acnes injection can induced specific CTL to stomach cancer cell in vitro. It has significant kill effect on stomach cancer cells and high level secretion.of INF-r.