Immunological Factor and Infertility

When treating couples with infertility, specialists have traditionally focused on testing for structural and hormonal abnormalities that interfere with conception. Recently, however, there has been a lot of attention given to the immune system as a possible cause of infertility in many couples. Fortunately, there are new tests that can help determine if your immune system could be keeping you from getting pregnant.

The Immune System

When your body encounters cells or particles that it does not recognize, such as foreign bacteria and viruses, it unleashes a massive response to first identify and then kill the unknown agent. This work is largely done by white blood cells, some of which have the ability to remember a particular invader so if you are ever infected by it again, your immune system is already prepared. Without these specialized cells, you would not be able to fight off infections and illnesses. Normally your immune system has the ability to tell the difference between the cells that should be in your body, and the ones that need to be destroyed. Sometimes, however, this part of the immune system breaks down, and the immune system actually turns on its own body.

The Immune System and Infertility

While it doesn’t seem like there would be a connection between the system that destroys other cells in your body and getting pregnant, the immune system actually is significant for implantation and development of an embryo. Certain inflammatory blood factors in the immune system help build up the wall of the uterus so that implantation occurs, and egg cells in the ovaries are surrounded by a fluid containing a high level of disease-fighting white blood cells. A woman’s antibodies, the cells that are specific to certain diseases or infections, are also transported across the placenta to the fetus, and are a developing baby’s first line of defense against infection both in the womb and after birth. Because the immune system is so intimately involved with fertility, when something goes wrong it can dramatically affect a woman’s ability to conceive and sustain a pregnancy. In fact some researchers believe that up to 20% of unexplained fertility cases may be caused by problems with the immune system.

The problems usually occur when a woman’s immune system produces a significantly larger amount of antibodies than normal. This overreaction of the immune system can cause antibodies to turn on things they would otherwise ignore, including eggs and developing embryos. There is evidence that suggests that an overactive immune system could play a significant role in recurrent miscarriage. Tests for specific antibodies are often included in an infertility workup for those couples that have been able to conceive, but are unable to sustain a pregnancy. In some cases, the antibodies will destroy an embryo before it even implants into the wall of the uterus. The hormones for pregnancy are produced after implantation, so pregnancy tests will never indicate that an embryo has formed, leading couples to believe that they just can’t get pregnant. Fertility related immunity problems also occur in men. A special barrier inside the passageways of the male reproductive system keeps sperm out of contact with the blood, which transports your immune cells. This protects the sperm by keeping them completely isolated from the killer white blood cells. If there is any injury or surgery that damages this blood-testes barrier, a man’s body can start producing cells that will kill sperm whenever they are in contact with the man’s own blood. Nearly 10% of infertile men have antisperm antibodies, compared with only 1% of fertile men. Fortunately, once it is diagnosed, immune related infertility is fairly easy to treat, and many couples conceive quickly after the problem has been addressed.

Future Work

The relationship between the immune system and infertility is still a new and relatively unproven area of reproductive medicine. The results of future research may solidify our understanding of the role the immune system has in our ability to get pregnant, and may offer new treatment options for the millions of people who receive a diagnosis of unexplained infertility.