Differential susceptibility of fresh Trichomonas vaginalis isolates to complement in menstrual blood and cervical mucus

The ability of complement in human menstrual blood and cervical mucus to kill Trichomonas vaginalis was compared with that of complement in serum, and 95 fresh trichomonal isolates obtained from vaginal wash material were evaluated for susceptibility to complement immediately after isolation. Only serum and menstrual blood with haemolytic activity produced total cytolysis of T vaginalis. The cytolytic abilities of these fluids were totally inactivated by treatment with heat or edetic acid (EDTA), which confirms the role of complement in cytolysis. Most cervical mucus samples had no detectable trichomonal cytotoxic properties. The cytotoxic activity in the remaining samples was not due to complement, as it was heat stable. Fresh isolates of T vaginalis and subpopulations of fresh isolates differed in their susceptibility or resistance to complement mediated lysis in serum. Resistance to complement did not remain stable after trichomonads were grown in vitro.