Hematopoietic cells of the intestine

Scientists have discovered a new source of blood cells in the human body

Dmitry Mazalevsky, Naked Science

In the last few years, researchers have begun to see in patients who have undergone intestinal transplantation, the presence of the so–called blood chimera - the production of their own blood cells adjacent to the cells of the donor. The results of the scientists' work could potentially facilitate subsequent transplants.

It is not known for certain exactly how much blood the intestinal tissue produces, but scientists suggest that the indicator can reach up to 10 percent of the total volume of blood in the body.

The preservation of blood cells can be expected one way or another from almost any transplanted organ, but the donor cells observed by scientists remained for a long time, which seemed very strange to them. To find out what happens to foreign cells for a long time, the discoverers of this strange secondary source followed 21 patients with intestinal transplantation for five years. 

During the observations, they not only managed to detect foreign hematopoietic stem cells and progenitor cells (HSPC) in the intestinal mucosa of the donor, but also to identify them in the small intestine, liver and lymph nodes. Moreover, over time, these cells were gradually replaced by the recipient's own hematopoietic tissues.

At first, this seriously excited scientists. White blood cells are the "infantry" of human immunity, it attacks foreign bodies that fall into their field of vision. The transplanted organ is not perceived by them as something "non-native", therefore, powerful drugs that resist rejection are needed to suppress the immune response. In addition, in such a situation, the so-called "graft versus host" reaction is also possible, associated with an immune conflict between donor and recipient cells. As it turned out, the opposite fractions of white cells somehow managed to "agree".

"In our study, we show that there is a kind of immune cross–dialogue between two sets of blood cells that protects the transplant from the patient's immune system and the patient from transplantation," says Megan Sykes, leader of the research group from the Columbia Center for Translational Immunology.

Graphic image of blood cells of the donor and recipient / © Megan Sykes

Intestinal allograft transplants have a high failure rate – about 50 percent during the first five years. Given the high load of lymphatic tissue in the organ, five to nine percent of patients may experience a "graft versus host" reaction. Such studies will allow us to learn more about this process and bring tangible benefits for future transplants.

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