Pregnancy and the Immune System

What happens to the immune system during pregnancy?

Although it is widely accepted that a fine-tuned interaction between maternal and fetal cells exists to support a healthy pregnancy, many studies have used mouse experiments to investigate this; But rats are not humans.

New research published in the Journal of Science Immunology sheds new light on how the human immune system changes as pregnancy progresses.

According to the World Health Organization (WHO), preterm birth, defined as birth before 37 weeks of gestation, is the leading cause of death in children under the age of 5. In 2015, this resulted in more than 1 million deaths worldwide. The number of preterm births is increasing globally. Survivors may face lifelong complications. So why does the immune system play such a big role in pregnancy?

Our bodies contain Human Leukocyte Antigen (HLA) genes, which help the immune system distinguish between the body's own proteins and those of a virus or bacteria. When a foreign protein is detected, the immune system starts working to defend us, as in the case of a cold or flu.

Some couples trying to conceive may be diagnosed with immunological incompatibility or allogeneic problems that are detrimental to their fertility. Genes transferred from both parents to the growing embryo cannot properly bind to the mother's immune system and the body may recognize the embryo as a foreign invader. As a result, the embryo may not be implanted or incorrect implantation may occur.

Diagnosing immunological infertility

A number of factors can affect a woman's ability to have a healthy pregnancy. Prediction of immunological abnormalities such as autoimmune disease, abnormal development of inflammatory cytokines in the mother's blood, elevation of activated immune cells, immune response to proteins in sperm, or inability of a mother to produce protective cells when pregnant Celiac disease, Crohn's disease, Multiple Sclerosis, Polycystic Ovary Syndrome (PCOS), Conditions such as Endometriosis and Lupus are some of the health problems that can lead to embryo rejection. Stress and nutritional factors may play a role in the mother's immune tolerance to pregnancy.

However, doctors can treat the patient in a way that creates tolerance to the embryo proteins. The most accurate method for diagnosing a couple's immune system problem; based on whole blood study panel and reproduction history. In addition to the data obtained, endometrial biopsy is also performed.

Pregnancy and the immune system; prevent immune-related miscarriages

First you need to make sure that there is no genetic cause for the miscarriage. If, after embryo transfer or miscarriage, a genetically healthy embryo detected prior to tissue analysis does not produce a healthy pregnancy, immunoassay testing should be considered to determine if there is an underlying immune cause for the woman's miscarriage. By determining the possible source of the problem, corrective treatments can be given. The aim is to help with the immune problem that needs to be created because genetic problems cannot be the only reason for miscarriage. As a result of this thought, the immune system is focused on as one of the most likely causes of miscarriage. In pregnant women with low immune system; the system will attack the embryo as if it were a foreign substance. And the embryo can be badly affected by this.

Patients who have experienced a miscarriage as a result of immune intolerance are usually recommended diet modification and a steroid protocol, along with certain medications, to help reduce the body's defensive response to the embryo.

Patients who did not become pregnant with good quality embryos, had a miscarriage of a genetically normal fetus, or had a miscarriage after a heartbeat were detected, should report these to their doctor if they have a family history of auto-immune diseases.

Immune system can fight against embryo

To allow the developing embryo to implant, some cells actively invade the lining of the uterus. This leads to an inflammatory process similar to those that occur during wound healing. If inflammation is prevented; implantation cannot progress, emphasizing the importance of inflammatory molecules and cells in this process.

This pro-inflammatory environment predominates during the first 12 weeks of pregnancy. During the next 15 weeks, the developing fetus is in a state of rapid growth and development. Anti-inflammatory cells and molecules dominate.

Some fetal cells express paternally derived cell surface markers or antigens. Under normal conditions, the mother's immune system perceives them as foreign and attacks the cells.

Regulatory T cells (Treg), a special form of white blood cell that promotes an anti-inflammatory environment, actively protect such fetal cells.

Low levels of T cells are linked to miscarriage

In the final stage of pregnancy, the immune system goes into a pro-inflammatory state. From now on, the mother cannot go into labor. Premature birth may be associated with abnormal immune responses.

A number of factors influence how the immune system behaves during pregnancy, and increasingly the mother's microbiome (beneficial organisms) begins to play a role.

Pregnancy and the immune system; Are viruses at the center of complications?

Viruses can take away the beneficial effects of normal microbiomes, putting the mother and fetus at risk. Viruses inactivate the immune system and immune signaling processes crucial to the interaction between bacteria. This puts the mother at risk of bacterial infection in addition to the virus that was previously in the system.

A mouse experiment showed that exposing the pregnant mouse to a common bacterial toxin over a viral infection caused preterm birth. In fact, 40% of human preterm births are associated with some type of infection.

In addition, viral and bacterial infections during pregnancy; It is associated with an increased risk for schizophrenia, autism spectrum disorder, and allergies later in life.

What could be the reason? Scientists have found that a high level of activation of the mother's immune system in response to an infection; feels responsible for causing irreversible damage to the fetus. Levels of inflammatory markers in the fetus indicate such conditions, even if an infection is not directly transmitted by the mother.

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