Are women more susceptible to STIs than men? With genital herpes infecting one in five women compared to one in ten men in the United States, and with women accounting for two out of three new HIV infections in sub-saharan Africa, the answer is yes. Women are more susceptible to many STIs including gonorrhea, chlamydia, HIV and others in comparison to men and the underlying reason for increased rates of infection could be due to the role female sex hormones play in the immune system of the female reproductive tract.
As a region of the body that must be receptive to foreign semen and to the implantation of fetuses for reproduction, the female reproductive tract undergoes changes in its immune regulation at different points of the menstrual cycle in order to provide an optimal environment for reproduction. Under the influence of differing levels of estrogen and progesterone, changes in mucus, inflammation, cell signaling, and immune cell numbers and phenotype lead to different immune responses at different points in the menstrual cycle. During the follicular phase, when progesterone levels are minimal, women tend to have higher levels of antibodies and increased inflammatory responses. In contrast, high levels of progesterone in the luteal phase have been associated with decreased inflammatory responses and a suppression of the immune system. In addition, increasing estrogen levels may also lead to relaxation of tight junctions in the epithelium right before ovulation in preparation for implantation and thus may make women more susceptible to infections. From the study from Wira, Garcia and Patel, this has been hypothesized as the “window of susceptibility” that makes women more susceptible to STIs.
Further understanding of the changes and mechanisms by which the immune system is regulated and compromised in the female reproductive tract will be crucial to formulating new vaccines or preventative methods that protect women from infection.
Sources:
Wira, C. R., Rodriguez-Garcia, M., & Patel, M. V. (2015). The role of sex hormones in immune protection of the female reproductive tract. Nature Reviews. Immunology, 15(4), 217–230.http://doi.org/10.1038/nri3819
This reminds me of a comment Dr Badtke made during our first embryology lecture about how pregnant women are not supposed to eat cold cuts due to the danger of infection of Listeria bacteria from potentially contaminated foods. She had mentioned that this was a particular concern due to the fact that pregnant women are immunosuppressed. I actually had done some reading regarding this after that and overall noted that though the immune system is in constant flux during pregnancy, there are times during the gestational period that the woman’s immune system is additionally suppressed and leave her more susceptible to sickness or infection. So it is not just the changes in immune regulation during the menstrual cycle that leave women more susceptible to STIs. This opens up the risk of affecting the fetus as well, or course, if a woman is infected during her pregnancy, which was the reason the outbreak of Zika was so forefront in our media coverage in recent years.
ReplyDeleteThough published all the way back in 2005, here’s a relevant study that found that in their sample the risk of HIV aquisition was higher during pregnancy, but was not likely due to sexual behaviors and instead due to hormonal changes. Interesting stuff!
https://www.sciencedirect.com/science/article/pii/S0140673605674818
This is very interesting! How do modern day birth control methods affect women's immune responses? Would the birth control pill increase or decrease a woman's susceptibility as compared to her immune responses before taking the pill? I found an interesting study that evaluates cell-mediated immunity in women taking an oral contraceptive compared to a control group. The women taking estrogen-progestogen combination pills showed similar percentages of B and T lymphocyte subpopulations compared to the control group, but their levels of total haemolytic complement (CH5O) were significantly different. The women's lower CH5O levels suggest that the birth control pill may alter a woman's complement system and circulating immune complexes (Ramalakshmi, 1979).
ReplyDeleteRamalakshmi, B. A., Jagadeesan, V., & Prema, K. (1979, October). Immune studies in oral contraceptive users. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/315858
I agree, this information is fascinating! It made me think of explaining the nature of human papilloma virus (HPV) to patients' and their confusion at the virus' ability to disappear and reappear. From what we know so far, this can either be the virus laying "dormant," similar to Herpes Simplex Virus, and resurfacing, or the patient could truly clear this viral strain and be reinfected with another. After reading your article, I wondered whether it would eventually influence when we test women for HPV: would it be better to wait until their immunity is low, to make sure it is not covering up any viruses? I ended up finding a study that showed that Estrogen, while it can help prevent initial HPV infections, may play a role in the link between an HPV infection and cervical cancer.
ReplyDeleteBrabin, Loretta. “Interactions of the Female Hormonal Environment, Susceptibility to Viral Infections, and Disease Progression.” AIDS Patient Care and STDs 16, no. 5 (May 1, 2002): 211–21. https://doi.org/10.1089/10872910252972267.
The first thing that came to mind for me is what are the implications for menstrual fluid during the first five days of the menstrual cycle. I've read that during menses, the chance of getting an STI is much higher because it may be easier for some pathogens to reach the upper cervix and the uterus due to the cervix being more open. But I also read that women typically abstain from intercourse during this time. I'm just wondering why luteal phase and the follicular phase differ so much since they are both before and after the menstrual phase. Does it have to do with the fact that there was menses?
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