Small organs can play an important role in the immune system during pregnancy |

The researchers studied the role of the thymus, or the hair, in the regulation of the immune system during pregnancy. The tymus plays a central role in the development of a very important group of immune cells, the T cells (the thymus). T cells act as a kind of driver that determines the immune system's response. Body cells must be tolerated, while foreign substances such as bacteria and viruses must be attacked.

Despite the central role of the thymus in the immune system, it is not known whether the function of the thymus changes during pregnancy. Current knowledge on the tymus comes mainly from studies conducted in mice. According to animal studies, the general perception is that the size of the thymus decreases during pregnancy and the outflow decreases, so that fewer T cells are released from the thymus.

Immune system weakened in animals but not in humans
In animals, a reduced amount of T cells causes weakening of the immune system, resulting in fetal tolerance. But does it work the same way in humans? To answer this question, the researchers studied the release of different types of T cells in the blood of 56 pregnant and non-pregnant women. A particular type of T cells, called regulatory T cells, is particularly interesting because they can inhibit other immune cells and prevent them from attacking the body's own tissues.

– We show that women have a continuous flow of thymus T cells during pregnancy. We also noted that the flow of regulatory T cells capable of suppressing the immune response appears to increase during pregnancy. The findings may explain why there is both fetal tolerance and ongoing defense against infection, "said Sandra Hellberg, PhD student in the Department of Clinical and Experimental Medicine and one of the researchers behind the study. .

May be important for autoimmune diseases
The discovery may also prove important for some autoimmune diseases, where the immune system has begun to attack the body's own cells. Many autoimmune diseases are related to the functioning of the thymus, such as multiple sclerosis (MS), where the brain and spinal cord are damaged by the immune system.

"At MS, previous research had shown a decrease in thymic function and a decrease in the number of T-cells released, which could explain why MS symptoms often improve during pregnancy," she says. Professor Jan Ernerudh, Head of Studies.

The research team is now considering examining the role of the thymus in women with MS who followed before, during and after pregnancy to determine whether changes in the balance between different types of T cells could explain why women with MS often improve during pregnancy.

The study was conducted in collaboration with the Linköping University Hospital, Mödrahälsovården of Vrinnevisjukhuset of Norrköping and the Karolinska Institutet of Stockholm. The research was funded with support from, among others, the Swedish Research Council and the South-East Swedish Research Council, FORSS.

L & # 39; section:
"Maintaining the Thymic Production of Conventional and Regulatory T Cells in Pregnancy", Sandra Hellberg, Ratnesh B. Mehta, Anna Forsberg, Göran Berg, Jan Brynhildsen, Ola Winqvist, Maria C. Jenmalm and Jan Ernerudh, (2018), Journal of Allergy. and Clinical Immunology, published online Oct. 9, 2018, doi: 10.1016 / j.jaci.2018.09.023

Contact:
Sandra Hellberg, PhD student, [email protected]
Jan Ernerudh, professor, [email protected]