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Study shows some blood stem cells better than others at resisting systemic disruptions like aging

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Blood stem cells produce approximately 10 billion new white blood cells —  also known as immune cells —  in your body each day. Even more remarkably, if some of these blood stem cells fail to do their part, other blood stem cells pick up the slack and overproduce whichever specific type of immune cell is lacking, according to a new University of Southern California (USC) study published in EMBO Reports.

Lisa Nguyen, a Ph.D. student in the lab of Rong Lu, Ph.D., and her colleagues observed this phenomenon by tracking individual blood stem cells that reside in the bone marrow of mice. To create the tracking labels, the scientists attached a unique piece of genetic code to each blood stem cell. During blood production, each blood stem cell passes its unique genetic label onto its progeny — which include two types of immune cells known as B cells and T cells.

The team then performed a series of bone marrow transplantations in mice to test the contributions of these uniquely labeled blood stem cells. Mice received a combination of normal blood stem cells and deficient blood stem cells with a genetic mutation that prevented them from producing either B cells only or both B and T cells.

The scientists found that the normal blood stem cells compensated for the B and T cell deficiencies. When co-transplanted with B-deficient stem cells, the normal stem cells overproduced B cells to keep the immune system in balance. And when co-transplanted with B- and T-deficient stem cells, the normal stem cells compensated by overproducing both B and T cells to maintain a balanced immune system.

The scientists also found that a few specific blood stem cells were doing most of the work. These key blood stem cells proliferated dramatically to compensate for the immune cell deficiencies in the recipient mice, and these cells continued to proliferate when they were transplanted into different recipient mice. These highly productive blood stem cells also showed changes in gene activity that enhanced their ability to oversupply deficient types of immune cells.

“These stem cells’ ability to compensate provides some degree of resilience to disruptions of the blood and immune system — such as the aging process, the early stages of many blood cancers and disorders, and bone transplantation,” said Dr. Lu, an assistant professor of stem cell biology and regenerative medicine at USC. “By understanding and ultimately harnessing this innate capacity of stem cells, we can potentially optimize treatments for a wide range of diseases.”

 

During blood production, each blood stem cell passes its unique genetic label onto its progeny — which include two types of immune cells known as B cells and T cells (above). Image courtesy of NIAID/NIH.

 

Learn more:

https://news.usc.edu/143798/how-the-body-balances-its-immune-system/

DOI 10.15252/embr.201745702