The Influence Of Myeloid-derived Suppressor Cells On B Cells In Breast Cancer

Objective: This study is aimed to explore the functions of MDSCs in breast cancer on B cells, further discussing the regulation mechanism of MDSCs on B cells.Methods: First, we have set up the 4T1-BALB/C mice breast cancer model, then test the change of spleen cells in the tumor-bearing mice. Then we use CD19 as the specific phenotype of B cells, use Gr-1 and CD11 b as the specific phenotype of MDSCs, we detected the percentage of tumor derived MDSCs and B cells in spleen by flow cytometry technology. Also, we compare the expression of 4-1BBL?CD80?CD86?MHC??CCR6?CD62L?PD-1and PD-L1 in B cells acquired from the spleen and blood of tumor-bearing mice and normal mice. Through the magnetic bead separation technology, we sort the Gr-1+ MDSCs from the spleen cells of the tumor-burdened mice, and sort the CD19+ B cells from the spleen cells of the normal mice. We coculture the MDSCs and B cells in vitro with the ratio of 3:1 and 5:1, at the same time set B cells as control. Then we detect the change of phenotypic moleculars 4-1BBL?CD80?CD86?MHC??CCR6?CD62L?PD-1and PD-L1 expressing on B cells by flow cytometry. We also detected the proliferation of B cells by Brdu technology. Finally, we collected co-culture supernatant and detect the secretion of Ig A, Ig M and Ig G in B cells.Results: In the 4T1-BALB/C mice breast cancer model, the length, weight and cell number of spleen cells are increased as the tumor growing, the proportion of MDSCs in spleen is obvious increased and the proportion of B cells is decreased, reaching the lowest at day 21. Flow cytometry experiments showed that the B cells phenotypic molecules CD86?MHC??CCR6?CD62L?PD-1and PD-L1 coming from the spleen of the tumor-bearing mice is obvious lower than that in the normal mice,4-1BBL?CD62L?PD-L1 and MHC?expressing on B cells coming from the blood of the tumor-bearing mice is also decreasing. In the co-culture experiments of MDSCs and B cells in vitro, we found that the changes of B cells' phenotype are same with the changes of B cells in tumorbearing mice, which shows that MDSCs might influence the function of B cells. After coculture, the proliferation of B cells is significantly decreased compared with the control group.The ELISA results show that, compared with the control group, the concentration of Ig M is significantly declined,while the Ig A and Ig G secretion is obvious increased in B cells.Conclusion: MDSCs in cancer maybe inhibit the normal immune function of B cells, and induce the secretion of Ig A and Ig G, and inhibit the secretion of Ig M.