How does the immune system cause infertility?

The immune system may produce antibodies or activate cells that mistakenly target reproductive cells or tissues, disrupting conception or pregnancy.

What are the main types of immunological infertility?

The main types include antisperm antibodies, antiphospholipid syndrome (APS), hereditary thrombophilias, alloimmune implantation dysfunction, and thyroid autoimmunity.

Immunological Infertility: Causes, Types, and How It Affects Pregnancy

Immunological infertility is a type of infertility caused by problems in the immune system. In simple terms, your body mistakenly treats sperm, eggs, or even an embryo as harmful invaders. Instead of supporting reproduction, the immune system reacts against it. This response can prevent pregnancy or make it harder to carry one to term.

Immunological infertility is complex and still being studied. It often overlaps with other fertility issues and may not be easy to diagnose. Some people may go through multiple tests or even failed treatments before finding out the immune system is involved. This condition can affect both men and women, and understanding its types and causes is the first step toward addressing it.

Understanding Immunological Infertility

Your immune system is like a guard, always on the lookout for invaders like bacteria or viruses. It uses white blood cells, called lymphocytes, to identify and neutralise these threats by producing antibodies. Normally, this system works smoothly to keep you healthy. But sometimes, it gets confused and starts attacking your own body’s cells, including those needed for reproduction. This mix-up can interfere with sperm, eggs, or even an embryo.

For example, in women, the immune system might see sperm or an embryo as a foreign invader and attack it. In men, it might target sperm, reducing their ability to fertilise an egg. This condition is thought to be behind about 20 per cent of unexplained infertility cases. It’s a significant but often overlooked issue.

How the Immune System Affects Fertility

This is how your immune system might affect your fertility or pregnancy:

Attacking sperm: In both men and women, the immune system can produce antibodies that target sperm. These antibodies may kill the sperm or stop them from moving properly.
Rejecting the embryo: During pregnancy, an embryo is a unique mix of your genes and your partner’s. This can confuse the immune system and trigger a reaction. Normally, the embryo releases signals, like HLA-G antigens, to calm the immune system and prevent attacks. But if this immune tolerance fails, the body may reject the embryo and leading to implantation issues or miscarriage.
Targeting the placenta: The immune system might attack the placenta, which is crucial for nourishing the developing baby. This may cause complications like miscarriage or poor foetal growth.

Types of Immunological Infertility

Immunological infertility comes in different forms, each with its own way of affecting fertility. These are the main types you should know about:

Antisperm antibodies (ASA): These antibodies attack sperm, making it hard for them to move or fertilise an egg. In men, ASA can form due to a rupture in the blood-testicular barrier (protective layer inside the testes). This can be caused by conditions like testicular torsion, varicocele, or infections. These antibodies show up in semen or blood. In women, ASA can develop due to conditions like endometriosis, sexually transmitted infections, or cervicitis, appearing in cervical mucus and blocking sperm from reaching the uterus.
Hereditary thrombophilias: This condition causes abnormal blood clotting due to genetic mutations that affect the body’s ability to regulate clotting. Blood clots can travel to the placenta and disrupt foetal development, increasing the risk of pregnancy loss.
Antiphospholipid syndrome (APS): APS is an autoimmune disorder where the body produces antibodies such as lupus anticoagulant or anticardiolipin antibodies. These interfere with normal blood flow by causing clots to develop. When clots form in the placenta, they can lead to miscarriage or other pregnancy complications.
Alloimmune implantation dysfunction: In this case, the immune system sees the embryo as a foreign invader and produces antibodies to attack it. High levels of natural killer (NK) cells, which normally protect the body, can mistakenly target the embryo. This may cause implantation failure or recurrent miscarriages.
Thyroid autoimmunity: Even mild autoimmune thyroid disorders can disrupt hormone levels, and this can affect embryo development or the ability to maintain a pregnancy.

Causes of Immunological Infertility

The causes of immunological infertility can differ based on the type. Take a closer look at what might trigger these problems:

Autoimmune disorders: Conditions like antiphospholipid syndrome, celiac disease, and endometriosis can make the immune system more likely to attack reproductive cells or tissues. These disorders disrupt the immune tolerance needed for a healthy pregnancy
Natural killer (NK) cell overactivity: Overly active NK cells can attack an embryo before or shortly after implantation, mistaking it for a threat. This is a common cause of recurrent pregnancy loss.
Genetic mutations: In hereditary thrombophilias, genetic changes affect how the blood clots. This can lead to clots that damage the placenta and prevent foetal growth.
Infections or trauma: In men, conditions such as testicular torsion or seminal infections can damage the blood-testicular barrier. This may cause the immune system to create anti-sperm antibodies. In women, infections like sexually transmitted diseases or cervicitis can also trigger immune reactions that affect fertility.
Hormonal imbalances: Autoimmune thyroid disorders can throw off the hormonal balance needed for ovulation, embryo implantation, and a healthy pregnancy.

Immunological infertility can be difficult to detect but plays a major role in many unexplained fertility problems. Its causes can make conception feel like an uphill battle, but knowing what’s behind the issue is the first step toward finding solutions. Talking to a specialist about immunological causes could be of great help if you’ve been struggling with unexplained infertility or recurrent miscarriages.

FAQs on When Your Own Immunity Affects Fertility: What to Know

How does the immune system cause infertility?
The immune system may produce antibodies or activate cells that mistakenly target reproductive cells or tissues, disrupting conception or pregnancy.
What are the main types of immunological infertility?
The main types include antisperm antibodies, antiphospholipid syndrome (APS), hereditary thrombophilias, alloimmune implantation dysfunction, and thyroid autoimmunity.