The importance of thymus gland and healthy pregnancies
Posted on January 29, 2021 at 2:00 PM
The importance of thymus gland and healthy pregnancies
The immune system of a pregnant woman is altered during pregnancy, but not in the way previously believed. Many studies have shown that the thymus, an organ of the immune system located close to the heart, plays an important role during normal pregnancy in ensuring that the mother's immune system protects against infection while at the same time tolerating the fetus.
The thymus as key to healthy pregnancies. An international research team led by the University of British Columbia (UBC) has uncovered for the first time the importance of a small gland tucked behind the sternum that works to prevent miscarriage and diabetes in pregnant women. The organ in question is the thymus, identified in a study published today in the journal Nature as playing a significant role in both metabolic control and immunity in pregnancy.
How the immune system adapts to support mother and fetus has puzzled by researchers for decades. The researchers have found that female sex hormones instruct important changes in the thymus, a central organ of the immune system, to produce specialized cells called Tregs (also known as regulatory T Cells) to deal with physiological changes that arise in pregnancy.
The researchers also identified RANK, a receptor expressed in a part of the thymus called the epithelium, as the key molecule behind this mechanism. The absence of RANK prevented the production of Tregs in the thymus during pregnancy. That resulted in fewer Tregs in the placentas, leading to elevated rates of miscarriage.
The findings also offer new molecular insights into the development of diabetes during pregnancy, known as gestational diabetes, a disease that affects approximately 15% of women in pregnancy worldwide, and about which scientists still know little.
In healthy pregnancies, the researchers found that Tregs migrated to the mother's fat tissue to prevent inflammation and help control glucose levels in the body. Pregnant mothers lacking RANK had high levels of glucose and insulin in their blood and many other indicators of gestational diabetes, including larger-than-average young. The deficiency of Tregs during pregnancy also resulted in long-lasting, transgenerational effects on the offspring.
The discovery of this new mechanism underlying gestational diabetes potentially offers new therapeutic targets for mother and fetus in the future. The thymus changes massively during pregnancy and how such rewiring of an entire tissue contributes to a healthy pregnancy has been one of the remaining mysteries of immunology.
The work of researchers over many years has now not only solved this puzzle “pregnancy hormones rewire the thymus via RANK” but uncovered a new paradigm for its function: the thymus not only changes the immune system of the mother so it does not reject the fetus, but the thymus also controls metabolic health of the mother.
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