IFNG and sexually transmitted disease: Compared with the SFI group, the average S protein specific T cell responses (IL-2, TNF-α and IFN-γ) of both the SSTI and the STI groups tended to be higher (Figures 5A, B), of which the frequencies of IFN-γ+CD8+ T cells (Figure 5A) and IFN-γ+CD4+ T cells (Figure 5B) were found to be significantly improved in the SSTI group.