| Background:The pathogenic mechanism of Treponema pallidum is not clear.TpFl is a very important protein of Treponema pallidum.The high expression of TpF1 protein can be detected in the serum of syphilis at all stages.Dendritic cells(DCs)are the only specialized antigen-presenting cells capable of initiating an immune response from newborn naive T cells.This paper discusses the influence of TpF1 on DC function.Methods:A total of 74 syphilis patients and 41 healthy subjects admitted to the Affiliated Zhongshan Hospital of Xiamen University from January 2020 to December 2020 were recruited.The number of DC1(CD 11 c+)and DC2(CD 123+)and the expression of surface markers CD80,CD86,CD83 and CD40 in peripheral blood of syphilis patients and healthy subjects were detected by flow cytometry.Human peripheral blood monocytes were induced into DC cells,and different concentrations of TpF1 were co-cultured with immature DC(iDC)to detect the expression of CD80,CD86,CD83 and CD40 on the surface of DC cells.The mRNA and protein expressions of IL-1β and IL-6 secreted by DC cells after co-culture of TpFl and DC cells were detected by RT-PCR and ELISA.DC was co-cultured with mixed lymphocytes,and the proliferation of lymphocytes in the mixed lymphocyte culture was detected by CCK8.Results:Ⅰ.The total number of DC,the absolute count of DC1 and the ratio of DC1/DC2 in the newly diagnosed group were significantly higher than those in the healthy group(P=0.033,P=0.005,P<0.001);The absolute count of DC2 and percentage of DC2 were significantly lower than those of healthy group(P=0.012,P=0.005).There was no significant difference between the total number of DC,absolute count of DC1,absolute count of DC2 and percentage of DC2 in the syphilis group after treatment and the healthy group(P=0.987,P=1.000,P=0.073,P=0.118).The expression of CD80 and CD40 in DC 1 of newly diagnosed syphilis group was higher than that of healthy body examination group(P=0.003,P<0.001).Compared with the newly diagnosed syphilis group,the mean fluorescence intensity of CD80 on the surface of DC1 cells in the syphilis group after treatment(1793±518)was significantly decreased(P=0.008).;The expression of CD40 was slightly downregulated,but the expression of CD40 on DC1 cells in the syphilis group was still significantly higher than that in the healthy body test group after treatment(P=0.021)。2.When the concentration of TpF1 increased from 500ng/mL to 10μg/mL,the cell death rate significantly increased from(6.40±0.22)%to(18.63±0.97)%.The mean fluorescence intensity of CD80,CD86,CD83 and CD40 expressions on DC cells stimulated by TpF1 500ng/mL for 48 hours showed no difference compared with that of unstimulated iDC cells,and were all lower than that of positive control LPSstimulated iDC cells,which were reduced by 1 times,1 times,1.5 times and 1 times,respectively(P<0.001,P<0.001,P=0.001,P<0.001):IL-1β mRNA and protein levels were reduced by 2.7 and 2.6 times,respectively(P=0.008,P=0.004),IL-6 mRNA and protein levels were reduced by 4.8 times and 11 times,respectively(P=0.020,P=0.014).Compared with iDC without TpF 1,the OD values of iDC treated by TpF 1 and allogenmixed lymphatic co-culture showed no difference at 24,48 and 72 hours,and were 0.6 times,0.3 times and 0.3 times lower than those of the iDC group stimulated by LPS 250ng/mL,respectively(P<0.001,P=0.012,P=0.026).Compared with 250ng/mL LPS stimulation,the expression of CD80 on DC cell surface decreased by 0.24 times and the expression of CD86 average fluorescence intensity decreased by 0.4 times.Conclusions:1.There is an imbalance of DC 1/DC2 subsets in syphilis patients.2.TpF1 inhibited the expression of CD80,CD86,CD83 and CD40 during iDC cell maturation,and weakened the activation function of DC cells to T lymphocytes.3.The expressions of IL-1β and IL-6 secreted by TpF1-induced iDC cells during the maturation process were lower than those of iDC cells treated with LPS alone.4.The low concentration of TpF1 can down-regulate the expression of CD80 and CD86 during the maturation of iDC cells. |
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