Host defences in the upper genital tract of the female: studies in a murine system

Mechanical and cellular factors which maintain sterility in the fallopian tube were studied in virgin, BALB/c mice. Quantitative cultures of homogenates from ovary/periovarian sac, fallopian tube and uterine horn were obtained at various times after intratubal injection of 6 X 10(7) Escherichia coli (E. coli) by micropuncture. Immediately post-injection, significantly higher bacterial counts were obtained from fallopian tube than from uterine horn, indicating a functional barrier at the uterotubal junction. Viable E. coli were usually absent from the genital tract within 7 days. Reduction in bacterial counts was significant at 24 h post-injection. Ligation of the uterine horn and/or induction of leucopenia prior to injection were associated with decreased bacterial clearance at 24 h. Histology of samples from normal, injected mice revealed marked polymorphonuclear leucocyte (PMNL) infiltration in response to E. coli, confirmed by quantitation of intralumenal PMNL. By 72 h post-injection, viable E. coli and PMNL containing phagocytosed particles were prominent in vaginal washings. No inflammatory response was elicited in leucopenic mice. We conclude that clearance of E. coli from the fallopian tube depends primarily on excretion through the lower genital tract and PMNL-associated bacterial activity.