Regulatory B Cells Production And Characteristic Induced By Schistosoma Japonicum Soluble Egg Antigens

In our country, Schistosomiasis is still one of the major public health problems. Schistosomiasis is a typical chronic infectious disease. In different stages of schistosome infection, the immune system produces different immune response to defend against various antigens from developmental stages of the schistosome. The solube egg antigen (SEA) and adult worm antigen (SWAP) are two major antigen components during the course of schistosome infection. Some studies have indicated that there are negative regulatory role during schistosome infection, and many studies have proved that the regulatory T cells can play a role in negative regulatory. Regulatory B cells are a class of of B cells and can secrete cytokines IL-10and/or TGF-β and other cytokines in autoimmune diseases, they can play an important role in chronic inflammation, cancer and parasitic infections. But whether SEA and SWAP can induce regulatory B cells and the mechanism of regulatory B cell production are still not clear. The purpose of this study includes (1) Investigate whether SEA and SWAP can induce regulatory B cells and the mechanism of Bregs production;(2) To further investigate the characteristic of Bregs induced by SEA. In this study, CD19+B cells were sorted by beads and were stimulated by SEA, SWAP, LPS in vitro, expression of CD80, CD86, CD40and the CD19+IL-10+B cells ratios were analyzed by flow cytometry after72hours. At the same time, the cytokines IL-10, IL-4, IFN-y and TGF-β levers in cultured supernatants were detected by ELISA. In vivo, mouses were immunized for three times with the mixture of SEA or SWAP or PBS and incomplete Freund’s adjuvant, respectively. The mouse spleen mononuclear cells were isolated, the CD19+IL-10+B cells ratios and the cytokines IL-10, IL-4, IFN-y and TGF-β levers in culture supernatants were analyzed at the seventh day after the last immunization. The relevant pathway blockers NF-κB、 ERK、JNK and p38MAPK were used and then cytokine IL-10lever was analyzed. Results showed that cytokine IL-10lever, the CD19+IL-10+B cells ratios in spleen mononuclear cells were significantly increased in groups stimulated by SEA and LPS, comparing to the SWAP stimulated group, In vivo, the cytokine IL-10lever、the CD19+IL-10+B cells ratios were significantly increased in SEA immunized group compared with the groups of SWAP and PBS immunization, whereas the cytokine IFN-y lever was significantly increased in groups in SWAP immunized groups, comparing to the SEA immunized groups. In vitro, the NF-κB、ERK、JNK and p38MAPK signal transduction pathway inhibitors inhibited the the IL-10secretion of B cells induced by SEA or LPS.In order to evaluate the characteristic of B cells induced by SEA, we sorted the B cells secreting IL-10induced by SEA or LPS, and the B cells secreting IL-10were co-cultured with CD4+T isolated from mouse splenic cell in the presence of medium or anti-CD3plus anti-CD28. Then cytokine levers of IL-4and IFN-y were analyzed after72h. The numbers of CD4+CD25+Foxp3+T, CD4+IFN-γ+T and CD4+IL-4+T cells were analyzed by FACS. Results showed that cytokine IL-4lever was incresed and the numbers of CD4+CD25+Foxp3+T and CD4+IL-4+T cells were also increased.The findings will help us to understand the process of negative regulatory in Schistosoma japonicum infection, and provide us new immunologic basis for further research of schistosoma infection.