Mysterious immune cells appear in the womb

Mysterious immune cells appear in the womb

Working to map every cell in the human body, an international team of scientists discovered a type of immune cell that appears first in the womb, and whose existence in humans has been hotly debated until now, Live Science reports, citing Science.

The mysterious cells, known as B-1 cells, were first discovered in mice in the 2018s, according to a 1 scientific review published in the Journal of Immunology. B-1 cells appear early in mouse development, in the womb, and produce different antibodies when activated. Some of these antibodies stick to mouse cells and help remove dead and dying cells from the body. Activated B-XNUMX cells also make antibodies that act as a first line of defense against pathogens, such as viruses and bacteria.

Beginning of human evolution

After B-1 cells were discovered in mice, a research group reported in 2011 that they found equivalent cells in humans, but these results were not accepted as conclusive evidence.

Thomas Rothstein, professor and founding chair of the Department of Investigative Medicine and director of the Center for Immunobiology at Western Michigan Medical School Homer Stryker, who was the first researcher in the previous study, said there was strong evidence that B-1 cells appear in early childhood. Human development, during the first and second trimesters of pregnancy.

Rothstein, who was not involved in the new research, added that the results of the latest study "confirm and extend previously published (research) work."

immune system development

Dr. Nicole Baumgarth, a professor at the UC Davis Center for Immunology and Infectious Diseases, who was also not involved in the new study, said she believes the new study's data and findings are "the most conclusive yet" and support the idea that humans carry B-1 cells, adding That in theory, B-1 cells could play critical roles in early development, and by studying them further, scientists are likely to improve their understanding of what the development of a healthy human immune system looks like.

Atlas of human cells

The new research is published alongside three other studies, conducted by the Human Cell Atlas Consortium (HCA), an international research group working to identify the location, function and characteristics of each type of cell in the human body. Together, the four studies include analyzes of more than one million human cells, representing more than 500 different types of cells from more than 30 different tissues.

While the lead researcher in the new study, Professor Sarah Tishman, Head of the Department of Cytogenetics at the Wellcome Sanger Institute in England and co-chair of the Organizing Committee of the Atlas of Human Cells, said that the studies are “Google maps of the human body, including an accurate display” of individual cells and their location. in tissues.

developing tissue

Professor Tishman and colleagues have recently focused their efforts on immune cells, and in particular, immune cells that emerge during early human development. The analyzes included cells from nine developing tissues, such as the thymus, a gland that makes immune cells and hormones, and the fetal yolk sac, a small structure that nourishes a fetus in early pregnancy. All tissue samples analyzed by the team came from Human Developmental Biology Resource, the UK tissue bank that stores human fetal and fetal tissue, with written permission from donors.

Thinner than human hair

Altogether, the data covered an early period of development from four to 17 weeks after fertilization, during the first and second trimesters of pregnancy. Professor Tishman said the researchers took high-resolution snapshots of this tissue at a scale of 0.001 inches (50 microns), which is thinner than a human hair. At the single-cell level, the team analyzed all of the 'RNA transcripts' in each tissue, which reflect the different proteins each cell makes. Using these texts, researchers can make inferences about the identity and function of each cell.

Through this detailed analysis, the team discovered cells that match the description of B-1 cells found in mice, in terms of their traits and timing of appearance.

B-2 . cells

“In the rat system, B-1 cells appear early — appear first,” Dr. Rothstein said. A different type of immune cell, appropriately called B-2, then emerges after the first B-1 cells and eventually becomes the most abundant form of B cell in the mouse. While Professor Tishman explained that immune cells can help sculpt new tissue as it forms.

Tissue trimming

Dr. Baumgarth said: "When you think about fetal development, in general, there's massive tissue remodeling going on all the time." For example, humans initially develop a webbing between their toes, but it fades again before birth. She said it's possible that B-1 cells help direct such trimming in tissues during development, but she said it was speculation on her part.

She went on to speculate that in addition to sculpting tissue, B-1 cells could provide some level of immune protection against pathogens small enough to cross the placental barrier.