Effects of B7-H3 on T lymphocytes in different activation states

Objective To study the impacts of B7-H3 molecule on the proliferation of T lymphocytes in different activation conditions and on the secretion of relevant cytokines. Methods Peripheral blood samples were collected from healthy subjects to separate peripheral blood mononuclear cells (PBMC) by Ficoll density gradient centrifugation. T lymphocytes were isolated from some of the PBMCs and purified with T Cell Enrichment Kit. PBMC and purified T lymphocytes were activated by anti-CD3/CD28 monoclonal antibodies (McAb) in vitro. Flow cytometry analysis was used to detect the expression of CD28 and CTLA-4 on T lymphocytes at different time points for further analyzing the activation states of T lymphocytes. On this basis, human B7-H3-Fc fusion protein was added into the mixed co-cultivation system on days 0, 1, 2, 3 and 4, and Hu-Fc fusion protein was used as isotype control. CCK-8 method was performed to detect the proliferation of T lymphocytes in each group. ELISA method was used to detect the secretion of cytokines (IL-2, IL-10 and IFN-γ) and to analyze the immune responses induced by stimulating T lymphocytes at different states of activation with B7-H3. Results B7-H3 molecule significantly inhibited the quiescent T lymphocytes from secreting IL-2 and IL-10, but had no significant impact on IFN-γ secretion. Moreover, it significantly promoted the activated T lymphocytes to secret IL-2 and IFN-γ, but had no obvious impact on IL-10 secretion. Results of the cell proliferation assay showed that B7-H3 molecule inhibited the in vitro proliferation of T lymphocytes in the PBMC, but had no obvious impact on purified T lymphocytes. Conclusion The regulatory effects of B7-H3 molecule on the immune functions of T lymphocytes vary with the activation states of T lymphocytes. Key words: B7-H3; T lymphocyte; Co-stimulatory effect