IFNG and chlamydia infectious disease: The increase in prevalent Chlamydia infection with increasing age among HIV-positive women in our study could be a result of either (i) immunobiological factors (i.e., low paucity of Lactobacillus spp., less acidic vaginal pH, and/or altered immune responses, including reduced levels of interferon gamma [IFN-γ] and interleukin-17 [IL-17] [57], as women age) or (ii) sexual behavior of the partner (since women aged ≥40 years reported a smaller number of new sexual partners).