Ten-year experience with antispermatozoal activity in ovulatory cervical mucus and local hydrocortisone treatment

Female sex hormones regulate the Th17 immune response to sperm and Candida albicans

STUDY QUESTION

What role do female sex hormones play in the antisperm immune response?

SUMMARY ANSWER

We found that sperm induce a Th17 immune response and that estradiol down-regulates the antisperm Th17 response by dendritic cells.

WHAT IS KNOWN ALREADY

Estradiol down-regulates the immune response to several pathogens and impairs the triggering of dendritic cell maturation by microbial products.

STUDY DESIGN, SIZE, DURATION

Ex vivo and in vivo murine models of vaginal infection with sperm and Candida albicans were used to study the induction of Th17 and its hormonal regulation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We analyzed the induction of Th17 cytokines and T cells in splenocytes obtained from BALB/c mice challenged with sperm and C. albicans. For the in vivo vaginal infection models, we used ovariectomized mice treated with vehicle, estradiol or progesterone, and we assessed the effect of these hormones on the immune response in the lymph nodes.

MAIN RESULTS AND THE ROLE OF CHANCE

Th17 cytokines and T cells were induced by sperm antigens in both ex vivo and in vivo experiments. Estrus levels of estradiol down-regulated the Th17 response to sperm and C. albicans in vivo.

LIMITATIONS, REASONS FOR CAUTION

This study was conducted using murine models; whether or not the results are applicable to humans is not known.

WIDER IMPLICATIONS OF THE FINDINGS

Our results describe an adaptive mechanism that reconciles immunity and reproduction and further explains why unregulated Th17 could be linked to infertility and recurrent infections.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by research grants from the Instituto de Salud Carlos III (ISCIII) (PI10/00897) and Fundación Mutua Madrileña to M.R. M.R. holds a Miguel Servet contract from the ISCIII (CP08/00228). M.A.M.-F. was supported by (ISCIII) INTRASALUD PI09/02029. We have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

Not required.

Sperm transport in the female reproductive tract

At coitus, human sperm are deposited into the anterior vagina, where, to avoid vaginal acid and immune responses, they quickly contact cervical mucus and enter the cervix. Cervical mucus filters out sperm with poor morphology and motility and as such only a minority of ejaculated sperm actually enter the cervix. In the uterus, muscular contractions may enhance passage of sperm through the uterine cavity. A few thousand sperm swim through the uterotubal junctions to reach the Fallopian tubes (uterine tubes, oviducts) where sperm are stored in a reservoir, or at least maintained in a fertile state, by interacting with endosalpingeal (oviductal) epithelium. As the time of ovulation approaches, sperm become capacitated and hyperactivated, which enables them to proceed towards the tubal ampulla. Sperm may be guided to the oocyte by a combination of thermotaxis and chemotaxis. Motility hyperactivation assists sperm in penetrating mucus in the tubes and the cumulus oophorus and zona pellucida of the oocyte, so that they may finally fuse with the oocyte plasma membrane. Knowledge of the biology of sperm transport can inspire improvements in artificial insemination, IVF, the diagnosis of infertility and the development of contraceptives.