Lactobacilli are strongly associated with reduced risks of infections by reproductive tract pathogens, including HIV-1 , HSV-2 Trichomonas vaginalis , Neisseria gonorrhoeae and Chlamydia trachomatis , as well as the multiple species of bacteria associated with bacterial vaginosis (BV) Lactobacilli are tolerated by vaginal epithelial cells and inhibit induction of pro‐inflammatory cytokines.
Increased exposure to the male ejaculate escalates a woman’s frequency of exposure to potential pathogenic microorganisms. Spermatozoa are viewed as foreign entities by the female. Frequent exposure to semen, therefore, increases the risk of development of antibodies to spermatozoa that can interfere with fertility. A lactobacilli‐rich vaginal microbiota appears to favour the establishment of tolerance that would diminish the likelihood of development of antisperm immunity. The immunosuppressive properties of seminal fluid also most likely contribute to the inhibition of sperm antibody formation. Although seminal fluid‐invoked immunosuppression may enhance the likelihood of male‐to‐female sexual transmission of pathogenic bacteria, this may be negated or minimised by lactic acid‐induced effects. Numerous studies have demonstrated that women with a lactobacilli‐dominated vaginal microbiota are at lower risk for a variety of infections than are women with a vaginal microbiota dominated by other bacteria.
