Maltose binding protein promotes dendritic cell maturation

【摘要】：Objectives:Maltose binding protein(MBP),a 42 kDa protein part of the maltose/maltodextrin system of E.coli,is often fused to relevant proteins to promote its yields,facilitate its purification by amylose affinity chromatography and enhance its solubility and stability.In recent years,it was found that MBP had immunoadjuvant activity.It can improve the immunogenicity of recombinant subunit vaccine.In addition,several studies have showed that MBP had extensive immunological activities including activation of NK cells,macrophages,or Th1 cells.The aim of the present study is to explore the regulatory effects of MBP on the maturation of dendritic cells(DC),so as to provide further evidence to clarify the cellular and molecular mechanisms of its immunoadjuvant activity.Materials and methods:1 x106 cells of DC2.4,a myeloid DC cell line originated from C57 BL/6 mice,were incubated in 24-well plate with different concentrations of MBP(0,1,5 ug/ml) for 24 h.The culture supernatants and cells were harvested for measurement of cytokines and flow cytometry analyses,respectively.Cytokines in the culture supernatants were measured by ELISA.Expression of CD40,CD54,CD80,CD86,MHC-I and MHC-II on the surface of DC were detected by flow cytometry.Results:The mean fluorescence intensities(AMFI) of CD40,CD54,CD80,CD86,MHC-I and MHC-II on the surface of DC2.4 in the control group were 23.45±1.68,335.15±6.55,3.54±0.36,60.75±4.18,250.15±5.43 and 64.35±6.02,respectively;in the 1 ug/ml MBP treatment group,the AMFI of CD40,CD54,CD80,CD86,MHC-I and MHC-H were 35.65±1.30,412.15±10.27,5.45±0.20,145.15±6.55,343.15±13.21 and 43.05±4.15,respectively;and in the 5 μg/ml MBP treatment group,the AMFI were 31.45±1.95,410.15±4.52,5.51±0.20,150.15±7.01,391.15±6.66 and 25.05±4.42,respectively.These data suggest that MBP promoted the expression of CD40,CD54,CD80,CD86 and MHC I on the surface of DC,while inhibited the expression of MHC-II compared with control group.The concentrations of IL-β,IL-6,IL-12 and IL-23 in culture supernatant of untreated DC2.4(control group) were 1025.50±35.36,311.9±27.02,18.4±1.15 and 2.3±2.08(pg/ml),respectively;the concentrations of cytokines in supernatants of 1 μg/ml MBP treatment group were 937.00 ±53.03,332.8±1.09,16.5±0.86 and 26.4±2.08(pg/ml),respectively;and the concentrations of cytokines in the 5μg/ml MBP treatment group were 945.50±21.21,311.13±21.58,16.5±2.29 and 31.4±2.12(pg/ml),respectively;suggesting that MBP stimulate the secretion of IL-23 of DCs compared with control group,while no significant changes were observed in IL-1β,IL-6 and IL-12 production.Conclusion:MBP promotes dendritic cell maturation.Our data provide further evidence to clarify the immunoadjuvant activity of MBP.