In murine models of genital C. trachomatis infection higher levels of IL-17/Th17 cells have been associated with greater pathology (Lu et al., 2012; Vicetti Miguel et al., 2016), whereas in IL-23 knock-out mice which had greatly reduced levels of IL-17 and IL-22 there was no difference in infection burden or oviduct pathology compared to wild type mice (Frazer et al., 2013). This evidence concerns the gene IL23A and infection.