What is reproductive immunology?

Reproductive immunology is a field of study that looks at how a woman’s immune system reacts when she becomes pregnant. Usually, your immune system works by fighting off any invading cells that it doesn't recognise because they don't share your genetic code. In the case of an embryo, the immune system learns to tolerate it even though it has a different genetic code from the mother.

Some scientists believe that in some cases of miscarriage or infertility, the mother’s immune system may fail to accept the embryo due to these differences in their genetic codes.

The immune system

The immune system is our body's protection against any invader. It defends the body against a wide range of pathogens including bacteria, viruses, other micro-organisms and to altered cells of our own body. It is a network of cells, tissues and organs that work together to defend the body against attacks by foreign invaders. Understanding how the maternal immune system responds to pregnancy is critical for our ability to better diagnose, understand and treat various pregnancy complications. This response of immune system to pregnancy is known as alloimmune response.

Immunological equilibrium

There is a balance between the activation and tolerance induced by the immune system. This immunological equilibrium is important for protection against autoimmune and alloimmune responses. Any disturbance in this equilibrium will lead to autoimmune or alloimmune disorders.

Fetus is a Semi-allograft

The fetus is 50% from the mother and 50% from the father. So, the fetus is 50% different immunologically from the mother. Hence, fetus is also known as “semi-allograft. In spite of this, the pregnancy continues to grow in the mother’s body without any rejection, as should have happened logically. This is known as “Paradox of pregnancy”. This is possible due to the complex immunological interactions happening at the feto-maternal interface.

Importance

Thus, Reproductive Immunology plays an important role in Implantation of embryo, continuation of early pregnancy and subsequent growth of pregnancy. Disturbances in Reproductive immunological mechanisms play a critical part in the causation of fertility related problems like repeated pregnancy loss, recurrent implantation failures and unexplained infertility. In fact, during the last 25 years, it has become clear that a large percentage of the unexplained repeated pregnancy loss/ recurrent implantation failures may be due to alloimmune cause. It has also been seen that more the number of miscarriages, more is the chance of alloimmune factor.

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