Molecular Diplomacy. From the attacks of the immune system of the mother, the fetus protects the cells of the "peacekeepers"
The human immune system is a unique "defense complex". The T cells that make up it provide protection against viruses and parasites, as well as carry out cleaning, getting rid of the damaged cells of the organism itself.
However, scientists for a long time could not understand why the mother’s immune system does not attack the fetus, because its DNA is different from the “native” one. The originated life, according to the logic of things, T-cells should be taken as "alien material."
A research team found the explanation from the Senger Institute (UK). It turned out that at the earliest stages of pregnancy in the body of a woman, the most complicated "molecular negotiations" take place, as a result of which the fetus receives "immunity".
According to scientists, in case of violation of such a "diplomatic agreement" during pregnancy, various complications can arise, including miscarriage. In addition, most of all threats are fraught with the first trimester.
Experts explain that in the very early stages of pregnancy, the uterine mucosa is transformed into decidual. The latter is one of the layers of the placenta. Decidual cells are rich in glycogen. This nutrient supports the development of the fetus.
According to the lead author of the work, Sarah Teichmann, the subtleties of interaction between the maternal body and the baby’s body at this stage have not been studied well enough. Meanwhile, they are crucial for the entire pregnancy.
The Teichmann team decided to consider the activity of the genes of individual cells of the mother and the fetus. Researchers collected data on the work of 70 thousand leukocytes and cells from the placental and decidual tissues of women who terminated the pregnancy between 6 and 14 weeks.
Using sngle-cell transcriptomics, they evaluated the activity of the genes of each cell and obtained information on the content of specific proteins.
As a result, the authors of the work identified 35 types of already known and not yet studied cells, including embryonic, which "occupy" the tissues of the mother and promote the formation of blood vessels between them and the fetus.
In addition, many types of immune cells have been discovered, including natural killer cells, which, as a rule, destroy infected and tumor cells.
Then, scientists reviewed the existing databases to determine which of the identified cells interact with each other based on protein bonds.
It turned out that invading mother tissue embryonic cells stimulate the production of specific immune cells that cause protective reactions.
Moreover, the researchers saw that some natural killers during such processes assume the role of "peacekeepers." They prevent the attack of other immune cells on the fetus and begin to produce chemicals that contribute to the development of the fetus and blood vessels.
As it turned out, the work of "peacekeepers" cells is controlled by one of the types of decidual cells known as stromal cells (one of the layers of the placenta is called the stroma, it is the connective tissue that contains the vessels).
"Now we can sort out in detail how [the cells] communicate with each other. Our results also demonstrate several levels of immunity regulation that were not previously taken into account," notes Sarah Teichmann.
Her research team has already created a database that works online so that colleagues from different countries can join the study of new data. As a result, specialists will be able to more closely examine the processes and mechanisms of life development in the early stages. In addition, more importantly, this information will help to understand the nature of various disorders during pregnancy and reduce the likelihood of complications.
Let me remind you that earlier another team of scientists obtained similar data, studying the early stages of the embryonic development of mice. Drawing an analogy with people, the authors of this study suggested that the new "settings" are preserved in the mother's body even after the birth of a baby. Therefore, during subsequent pregnancies, there are usually fewer complications.