The Quantitative And Functional Changes Of Natural Killer Cells In The Chronic Infection Of Treponema Pallidum

Objective To study the role of NK cells in Treponema pallidum infection and explore the possible mechanisms of NK cells in chronic of Treponema pallidum infection.The percentage of natural killer cells and their subtypes in peripheral blood of patients with different stages of syphilis were analized in the present study.Methods 1.Detection of NK cells and their subtypes in peripheral blood: We collected 10 healthy olunteers,14 secondary syphilis,12 latent syphilis and 14 neurosyphilis.Peripheral blood mononuclear cells were isolated.CD8 +T cells,NKT cell,NK cell numbers and NK cell subtypes,the expression of CD158 a and CD158e1 on NK cell were measured by flow cytometry.2.Detection of NK cell function: we collected peripheral blood from 5 healthy volunteers and 8 patients with secondary syphilis in this study.Magnetic bead absorption cell sorting(MACS)method was used to isolate the CD3-CD56+NK cell from the blood of secondary syphilis and healthy donors.Stimulated with K562 cells,IFN-γ+ and Granzyme B +NK cells were measured by flow cytometry.Under different E/T ratios,cytolytic activity of NK cells was tested by killing K562 cells.3.Statistical analysis: Data were analyzed using the statistical program SPSS 17.0.The values obtained from flow cytometry analysis were reported as the mean±standard deviation.Statistical comparison was tested using the Mann-Whitney test for unpaired nonparametric analyses and the Paired student T test for paired observations.A p value<0.05 was considered significant.Results 1.The percentage of CD3-CD56+NK cells in the peripheral blood of patients with secondary syphilis,neurosyphilis,and latent syphilis were significantly lower than that of control group(P=0.0035,P=0.01,P=0.006,respectively).The percentage of CD3+ CD56+NKT cells in peripheral blood of patients with secondary syphilis was significantly lower than that of the control group.while this percentage was not statistically different in patients with neurosyphilis and latent syphilis from normal control group(P=0.76,P=0.09,respectively).But the percentage of CD8+T cells in peripheral blood of patients with secondary syphilis,neurosyphilis,and latent syphilis was not statistically different from that in normal controls(P=0.27,P=0.09,P=0.46,respectively).2.The percentage of CD3-CD56 dimNK cells in peripheral blood of patients with secondary syphilis was(38.9±4.19)%,which was significantly lower than that of the normal control group [(54.9±5.9)%,P=0.03].While this percentage was not statistically different in patients with neurosyphilis and latent syphilis from normal control group(P=0.21,P=0.17,respectively).The percentage of CD3-CD56 brightNK cells in peripheral blood of patients with secondary syphilis,neurosyphilis,and latent syphilis was not statistically different from that of normal controls(P=0.11,P=0.19,P=0.06,respectively).While the percentage of CD3-CD56-CD16 dim NK cells and CD3-CD56-CD16 bright NK cells in peripheral blood of patients with secondary syphilis were significantly higher than that of control group(P=0.01,P=0.04,respectively).3.Stimulated with K562 cells,the percentage of IFN-γ+NK cells in secondary syphilis group and neurosyphilis group were lower than that in control group(P=0.0002,P=0.0015,respectively).The percentage of IFN-γ+ CD3-CD56 dimNK cells and IFN-γ+ CD3-CD56 brightNK cells were both decreased in secondary syphilis group and neurosyphilis group.The results of NK cells killing function showed that the proportion of killed K562 were no significant difference between secondary syphilis group and normal control group.After blocking with the addition of CD158 a antibody,the proportion of IFN-γ positive NK cells was higher in the CD158 a antibody closed group than that of without CD158 a antibody closed group,but there was no statistical difference between the two groups(P = 0.11).Conclusion 1.The percentage of NK cells in the peripheral blood of syphilis patients decreased,mainly the decrease of the percentage of cytotoxic NK cell subtypes,but the percentage of subtypes of NK cells with impaired immune function were increased,which suggested that Treponema pallidum might impaire the function of NK cells.2.The percentage of IFN-γ+ NK cells in peripheral blood of syphilis patients was decreased,suggesting that Treponema pallidum might inhibit the ability of NK cells to secrete IFN-γ,thereby reducing the ability of NK cells to regulate cellular immune responses.3.Treponema pallidum infection leads to decrease the number and inhibits the functions of NK cells,which might result in incompletely eliminate of Treponema pallidum and cause chronic infection.