C3 and chlamydia trachomatis infectious disease: The adequate amounts of C5bCt-9 produced in a short time in vitro relied on the co-existence of traditional C3-dependent C5 convertase cleaving at the R751 site, which appears to contradict the phenomenon that C3−/− mice have no resistance to hydrosalpinx after chlamydial infection (Yang et al., 2014).