ICOS and syphilis: Furthermore, among Tfh1 cells, Tfh2 cells, Tfh17 cells,central memory Tfh cells, effector memory Tfh cells, effector Tfh cells, naïve Tfh cells, and resting Tfh cells, only the percentages of ICOS+Tfh or the effector memory Tfh cells significantly increased in secondary syphilis but decreased in latent syphilis patients.