While working to map every cell in human body, Scientists have discovered an elusive type of immune cell that first appeared in the womb. The existence of such cells in humans has been hotly debated – until now.
These mysterious cells, known as B-1 cells, were first discovered in mice in the 1980s, according to a 2018 review in Journal of Immunology. These cells arise early in the development of the mouse, in the womb, and they give rise to many types antibody when activated. Some of these antibodies attach to the cells of the mouse and help remove dead and dying 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. bacteria.
After discovering B-1 cells in mice, a research team reported in 2011 that they found equivalent cells in humans, but these results should not be 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 University, was the lead author of the earlier work.
Now, a new study, published Thursday (May 12) in the journal Scienceprovides solid evidence that B-1 cells emerge during early human development, during the first and second rounds about three months. Rothstein, who was not involved in the new study, told Live Science: “It validates and expands on work that we’ve previously published.
“I think this is the most convincing data” to support the idea that “I think this is the most convincing data,” said Dr. Humans carry B-1 cells. In theory, these cells could play important roles in early development, and by studying them further, scientists can better understand the development of a healthy immune system. strong in humans, Baumgarth told Live Science.
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A rare look at the developing immune system
The new study is published alongside three others recently conducted by the Human Cell Atlas (HCA), an international research group working to define the location, function and characteristics of all types of cell membranes. cells in the human body. Together, the four studies – all published May 12 in the journal Science – include analysis of more than 1 million human cells, representing more than 500 distinct cell types sampled from more than 30 different tissues.
“You can think of it as a ‘Google Maps’ of the human body, and it’s really a ‘street map view’ of individual cells and where they’re located in the tissues that we’re targeting. coming,” said Sarah Teichmann, senior author of the study, chair of the Department of Cell Genetics at the Wellcome Sanger Institute in the UK and co-chair of the Human Cell Atlas Organizing Committee.
To help build this atlas of the human body, Teichmann and her colleagues recently focused their efforts on immune cells, and in particular, immune cells emerge during early human development. Through this work, they discovered evidence of human B-1 cells. “What we have shown is that they do exist in the human body,” Teichmann told a news conference on May 10.
Analysis of signature cells from nine developing tissues, such as the thymus, a gland that makes immune cells and hormones, and the embryo’s yolk sac, a small structure that nourishes the embryo in early pregnancy. All tissue samples analyzed by the team came from Human Development Biology, a UK-based tissue bank that stocks human embryonic and fetal tissues, with written permission from the donors. . They also incorporated publicly available data from previous HCA studies.
In general, the data cover the initial development period from 4 to 17 weeks after fertilization, so in the first and second trimesters.
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The researchers took high-resolution snapshots of these tissues, on a scale of 0.001 inches (50 microns), thinner than a human hair, Teichmann said during the press conference. And at the single-cell level, the team analyzed them all.”RNA copies” in each tissue, reflecting the different proteins each cell makes. Using these copies, researchers can make inferences about the identity and function of individual cells.
Through this detailed analysis, the team discovered cells that matched the description of B-1 cells found in mice, both in terms of their properties and the timing of their appearance.
“In the mouse system, B-1 cells arise early — they arise first,” says Rothstein. Another type of immune cell, appropriately called B-2, then emerged after the first B-1 cells and eventually became the most abundant form of B cell in mice. The new study suggests something similar happens in humans, where B-1 cells arise and are most abundant during early development, Rothstein told Live Science.
What purpose could these particular cells serve in a developing person? Teichmann says they can help create new tissues as they form.
“When you think about fetal development, there’s a massive remodeling of tissues going on all the time,” says Baumgarth. For example, humans initially develop a mesh between their fingers, but this membrane is trimmed back before birth. It is possible that B-1 cells help direct the pruning of such tissues during development, but “for my part, that’s speculation.”
In addition to sculpting tissues, B-1 cells may provide some degree of immune protection against pathogens that are small enough to cross the placental barrier, Baumgarth said. Again, this is speculation, she said.
The new study expands our understanding of how B-1 cells develop initially and could lay the groundwork for future studies of how cells function later in life, Rothstein said.
Originally published on Live Science.
https://www.livescience.com/newfound-prenatal-immune-cells Scientists finally have proof of mysterious immune cell in humans