by While working to assign each cell to human body, Scientists have discovered an elusive type of immune cell that first emerges in the uterus. The existence of such cells in humans has been hotly debated – so far.
These mysterious cells, known as B-1 cells, were first discovered in mice in the 1980s, according to a 2018 review in The Journal of Immunology. These cells appear early in the development of the mouse, in the uterus, and produce various antibodies when activated. Some of these antibodies attach to the cells of the mouse itself and help remove dead and dead cells from the body. Activated B-1 cells also produce antibodies that act as a first line of defense against pathogens such as viruses and bacteria.
Following the discovery of B-1 cells in mice, a research team reported in 2011 that they had found equivalent cells in humans, but these results were not accepted as conclusive evidence. “At that time, they were all over the place … Not everyone agreed with our profile on human B-1 cells,” said Dr. Thomas Rothstein, professor and founding president of the Department of Research Medicine and director of the Center for Immunobiology. Western Michigan University Homer Stryker MD School of Medicine, who was the senior author of this previous work.
Now, a new study, published in the journal Thursday (May 12th) Scienceprovides solid evidence that B-1 cells occur in early human development, within the first and second Semester. “It confirms and extends the work we have published in the past,” Rothstein, who did not participate in the new study, told Live Science.
“I think this is the most convincing data yet” that supports the idea that humans carry B-1 cells, said Dr. Nicole Baumgarth, a professor at the UC Davis Center for Immunology and Infectious Diseases, who did not participate in the new study. In theory, these cells could play critical roles in early development, and by studying them further, scientists could better understand what healthy immune system development looks like in humans, Baumgarth told Live Science.
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A rare look at the developing immune system
The new research was published along with three other studies recently conducted by the Human Cell Atlas (HCA) consortium, an international research team working to determine the location, function and characteristics of each cell type in the human body. Together, the four studies – all published May 12 in Science – include analyzes of more than 1 million human cells, representing more than 500 different cell types sampled from more than 30 different tissues.
“You can think of it as the Google Maps of the human body, and it’s actually a ‘view of the road maps’ of individual cells and the point that they sit in the tissues we are targeting,” said study leader Sarah Teichmann. Head of Cell Genetics at the Wellcome Sanger Institute in England and Co-Chair of the Human Cell Atlas Organizing Committee.
Helping build this atlas of the human body, Teichmann and colleagues recently focused their efforts on immune cells, and in particular, immune cells that emerge during early human development. Through this work they discovered elements of human B-1 cells. “What we are showing is that they do exist in humans,” Taichmann told a news release on May 10.
The assays included cells from nine developing tissues, such as the thymus, a gland that produces immune cells and hormones, and the fetal yolk sac, a small structure that nourishes the fetus. early pregnancy. All of the tissue samples the team analyzed came from Human Developmental Biology Resource, a tissue bank in the United Kingdom that stores human embryonic and embryonic tissues, with written permission from donors. They also incorporated publicly available data from previous HCA studies.
Overall, the data covered an early growth period ranging from four to 17 weeks after fertilization, ie within the first and second trimesters.
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The researchers took high-resolution snapshots of these tissues, at a scale of 0.001 inches (50 microns), which is thinner than a human hair, Teichmann told a news conference. And at the monocyte level, the team analyzed all “RNA transcripts “in each tissue, reflecting the different proteins produced by each cell. Using these transcripts, researchers could draw conclusions about the identity and function of each cell.
Through this detailed analysis, the team identified cells that matched the description of B-1 cells found in mice, both in terms of their characteristics and time of onset.
“In the mouse system, B-1 cells appear early – they emerge first,” Rothstein said. A different type of immune cell, aptly named B-2, appears after the first B-1 cells and eventually becomes the most abundant B-cell form in the mouse. The new study suggests that something similar is happening in humans, where B-1 cells appear and are more abundant in early growth, Rothstein told Live Science.
What purpose can these special cells serve in a developing human? They can help sculpt new tissues as they form, Teichmann said.
“When you think about fetal development, in general, there is a huge tissue remodeling that happens all the time,” Baumgarth said. For example, humans initially develop a mesh between their fingers, but this tissue is cut off before birth. B-1 cells may help cut tissue during growth, but “that’s my guess,” he said.
In addition to tissue sculpting, B-1 cells can provide some level of immune protection against pathogenic microorganisms that are small enough to cross the placental barrier, Baumgarth said. Again, that’s a guess, he said.
The new study broadens our understanding of how B-1 cells initially grow and could lay the groundwork for future studies on how cells function later in life, Rothstein said.
Originally published in Live Science.
