New Light Shed on Early Immune System Development

It's important to understand the human immune system. Implicated in various diseases, such as leukemia, the immune system is an important part of the human body. Now, scientists have shed light on how and when this system is formed, which may help future research concerning genetic diseases.

The immune system is complex, and a number of genetic diseases are attributed to defects in the cells that form its origins. In order to better understand this system, the researchers took a closer look at immune cells.

Researchers have long known that the first blood stem cells are formed in the aorta region and then travel to the liver, which is the body's major blood-forming organ during the fetal stage of development. In the liver, the blood stem cells produce the more mature blood cells that form our blood system. At the same time, T- and B-cells are formed, which comprise the basis of the advanced immune system. From birth, this process takes place in the bone marrow and the liver ceases to form blood cells.

In order to find out a bit more about the development of this immune system, the researchers examined mice. In the end, they found that the cells linked to our immune system are formed even earlier than thought. It turns out that the cells are formed in the embryo's yolk sac before the first blood stem cells are formed. In the human embryo, the yolk sac is one of the three fetal sacs and appears during the fifth week of pregnancy.

"The question we have posed is whether the immune system is formed in a different way in the fetus than in an adult and how early in the development of the fetus the cells that form our early immune system can be found," said Charlotta Boiers, one of the researchers, in a news release. "Knowledge of this is important because it helps us to understand how and when our immune system begins to form and what can go wrong in that process."

The findings could help researchers better understand conditions, such as childhood leukemia. In fact, scientists have shown in the past that the first mutation on the path to childhood leukemia occurs when the child is still in the womb, which means understanding development is crucial for potential prevention.

The findings are published in the journal Cell Stem Cell.