Your vagina’s immune system

Your vagina has its own immune system using the special cells that line the reproductive tract, the special fluid that coats them, and then the healthy microflora that fight invaders.

These components are each different, offering a specific set of defence mechanisms by which they protect the vagina.

Vaginal microflora and immunity

The microflora element is reasonably straightforward – you have a few types of good bacteria that live in the vagina, and fight invaders off and keep the environment acidic. Generally speaking, in most human populations, the predominant species is lactobacilli, but this can vary.

The microbes play a part in keeping the vagina healthy, protecting it from sexually transmitted infections, bacterial vaginosis, aerobic vaginitis, yeast infections and viruses.

While extremely important as a defence mechanism in the vagina, the vaginal microbiome is not the focus of this article. Here we’re discussing the vaginal cells and the special fluid that coats them, and how this acts for immunity of the vaginal cells.

The vaginal cells and immunity

These cells are called epithelial cells. Vaginal epithelial cells are your first line of defence against incoming pathogens, and their health – ability to fight for your vagina – depends on various factors.

The vagina is a unique mucosal environment with two functions: defending your reproductive tract, while being a means of reproduction. Because a vagina is a high-traffic area – lots of incoming and outgoings – it has to be unique in its structure and function.

That means your vagina has to protect you from incoming and already-present pathogens, trauma to tissue, and safely get sperm in and a baby out.

Understanding the structure of your vagina

The mucosal surface of your vagina and the outer portion of your cervix are protected by different layers of non-keratinised squamous epithelial cells.

They do not, however, produce mucous – these layers have no glands in them. The fluids in the vagina come from the cervix and uterus, and the vulva (Bartholin’s glands and Skene’s glands).

Your vagina has what’s known as rugae. Think of rugae as like an accordian, folding tissue, which can stretch right out to fit a baby. The surface area of the vaginal rugae is actually quite large.

• The outer layers of the vaginal epithelium are composed of superficial cells, which are loosely bound and sloughed off regularly and replaced
• Underneath the superficial cells are layers of intermediate and then basal epithelial cells

The basal membrane supports the basal layer, with the intermediate lying on top, and the superficial at the outermost side that you could see if you could look inside your vagina.

These cells come and go during a normal menstrual cycle, due to the effects of oestrogen. When there is high oestrogen, these cells all proliferate, and increase the number of cell layers. The cells go from being immature to mature, not as you age, but as they age.

There are some Langerhans cells and melanocytes in the vaginal epithelium too.

The complex fluid that coats your vaginal cells

The coating of fluid on your vaginal cells contains quite a lot of important components.

• Vaginal transudate (normal fluid pushed out of your blood vessels)
• Vaginal cells
• Bacterial products from healthy flora (lactic acid, metabolic wastes, defence mechanisms, etc.)
• Mucous and secretions from the cervix
• Secretions from the uterus and above (fallopian tubes, ovaries)

This fluid has lots of natural antimicrobials in it, which help protect the cells, including:

• Human beta-defensin 2 (HBD2) and HBD4
• Elafin
• CCL20/MIP3α
• Stromal-derived factor 1 (SDF-1α)
• IL-8
• Regulated upon Activation normal T-cell expressed and secreted (RANTES)
• Secretory leukocyte protease inhibitor (SLPI)
• Calprotectin
• Lactoferrin
• Lysozyme

The role of your vaginal cells and the coating fluid in immunity

Your vaginal and outer cervical cells are likely the first cells that greet incoming pathogenic microbes – that is, viruses, bacteria, protozoa, and yeasts. The fluid that coats them has many functions in protecting your vaginal cells from colonisation by pathogens, reducing and controlling inflammation, and keeping your tissue in good working order.

The fluid coating the vaginal cells plays a very important role, offering anti-HIV, anti-herpes (HSV2) and antibacterial activity by interacting with and inhibiting viruses and microbes.

The role of your hormones on your vaginal cells, and thus your vaginal immunity

Hormone levels cause fluctuations in the antimicrobials found in the fluid coating, meaning that at some times of a normal menstrual cycle, different levels of protection are offered.

Uterine changes in protection

• Proliferative phase (before ovulation) – HBD4 is highest
• During menstruation – HBD2 is highest, elafin concentration increases dramatically
• Late secretory phase – SLPI is highest

Vaginal changes in protection

There have been some studies that show that the concentrations of the antimicrobial qualities of the vaginal fluid were lowest at mid-cycle, when oestradiol levels peak, compared to other phases of the menstrual cycle. However, this has been contradicted by other studies that show no real changes to the antimicrobial content over the cycle.

This led researchers to believe that hormones are not the only dictators of what this fluid contains.

Optimising vaginal cell immunity

The best way to optimise your vaginal cell immunity is to work on your whole-body immunity. That will naturally affect your vaginal cells. This means eating well, sleeping well, managing stress, having a diet that suits your body (i.e. avoiding irritant foods/allergens, increasing fresh fruit and vegetables), and exercising as you are able. All good in theory, not so easy in practice for many of us.

It may also include taking certain supplements, herbal medicines or drugs that augment your immune response to enhance it as per your needs. This is a discussion between you and your healthcare practitioner. A naturopath or herbalist is a good place to start if your immunity has suffered a blow or ongoing onslaught.

References

• Patel MV, Fahey JV, Rossoll RM, Wira CR. Innate immunity in the vagina (part I): estradiol inhibits HBD2 and elafin secretion by human vaginal epithelial cells. Am J Reprod Immunol 2013; 69: 463–474
• Patel MV, Ghosh M, Fahey JV, Ochsenbauer C, Rossoll RM, Wira CR. Innate immunity in the vagina (Part II): anti-HIV activity and antiviral content of human vaginal secretions. Am J Reprod Immunol 2014; 72: 22–33