Peripheral blood mononuclear cells (PBMC) were stimulated and stained for flow cytometric analysis. Lymphocytes were gated according to forward and side scatter characteristics, and CD4+ T cells were gated based on CD3 and CD4 expression. (A) The percentage of total IL-17+ cells in gated lymphocytes in peripheral bloods of healthy donors (n = 70), syphilis patients without neurological disorders (including primary, secondary, latent and serofast syphilis; n = 69), and syphilis patients with neurosyphilis (n = 103) (including both asymptomatic and symptomatic neurosyphilis). (B) The percentage of Th17 cells in gated CD3+ T cells in peripheral bloods of the three groups shown in (A). (C) The percentage of Th17 cells in gated CD4+ T cells in peripheral bloods of the three groups shown in (A). (D) The percentage of total IL-17+ lymphocytes in gated lymphocytes in peripheral bloods of asymptomatic (n = 40) and symptomatic (including meningovascular, paretic, ocular and tabetic, n = 63) neurosyphilis patients. (E) The percentage of Th17 cells in gated CD3+ T cells in peripheral bloods of the two groups as in (D). (F) The percentage of Th17 cells in gated CD4+ T cells in peripheral bloods of the two groups as in (D). Each dots represents one individual. Results represent the median + individual values.