The Regulative Effect Of Costimulatory Molecules B7-H1on Immunosuppressive Function Of Myeloid-derived Suppressor Cells

Objective：As we age, the incidence of cancer and age-related diseases increases,reveals an relationship between aging and immunity. Myeloid-derived suppressor cells area group of powerful immunosuppressive cell population, which played a key role in tumorimmune escape. However, the relationship between aging and MDSCs function, especiallythe mechanism is not clear. Therefore, this study aims to explore the costimulatorymolecules (B7-H1) on myeloid-derived suppressor cells (MDSCs) in age-related immunesuppression in mice.Methods： Thirty-six young and aged C57BL/6J mice were selected for this study.The expression of costimulatory molecules on MDSCs was analyzed using flow cytometry(FCM). In order to understand the immunosuppressive functions of B7-H1on MDSCsfrom youth and elderly, we sorted MDSCs using MDSC Isolation Kit and grinded lymphnodes for T cells. T cell proliferation assay was determined in following groups includingT cells without carboxyfluorescein diacet ate succinimidyl ester (CFSE), T cells withCFSE, T cells with CFSE plus MDSCs from young mice, T cells with CFSE plus MDSCsfrom aged mice, and T cells with CFSE plus MDSCs from aged mice and anti-B7-H1blocking antibody, in mixed cultures provide stimulating with CD3and CD28signals.Then observed the difference of inhibition of T cell proliferation between each group, andevaluated whether B7-H1is the key molecule that causing the difference. Real-timefluorescence-based quantitative polymerase chain reaction (RT-PCR) was used to explorethe key gene for regulating the expression of B7-H1between youth and elderly. On thisbasis, in vitro MDSC stimulation assay was used to verify the regulatory mechanism of theexpression of B7-H1on aging MDSCs.Results：The population of Gr-1+CD11b+B7-H1+MDSCs was significantly higher in elder individuals when compared with that from young counterparts (P=0.017,statistically significant difference). T cells proliferation assay revealed that T cells werehighly suppressed by MDSCs from the aged mice (P=0.032, statistically significantdifference); however, this phenomenon was dramatically rescued by MDSCs from the agedmice with anti-B7-H1blocking antibody (P=0.014, statistically significant difference).RT-PCR and MDSC stimulation assay showed that IL-10(interleukin10), as one of theinflammatory factors, was the key factor for regulating the different expression of B7-H1between youth and elderly.Conclusions：Negative costimulatory molecule B7-H1plays an important role inregulating age-related immune suppression of MDSCs; Inflammatory cytokines IL-10is akey factor in regulating the expression of B7-H1between youth and elder MDSCs.