Blood Stem Cells Play Role in Immune Response

A new Harvard Medical School (HMS) study found that blood stem cells patrol the body’s organs, and, if exposed to infectious agents, have the capacity to participate in immune response.

In a paper published in Cell last week, HMS Immunopathology Professor Ulrich H. von Andrian and colleagues revealed that stem cells are more versatile and active than scientists previously thought.

Von Andrian, who led the research project, said he believes this discovery will help scientists understand how stem cell trafficking may be influenced by—and perhaps contribute to–various pathologies, such as inflammatory diseases and cancer.

Scientists have known for decades that stem cells sometimes migrate from the bone marrow into the bloodstream. But they have not yet understood the “meaning and consequences” of this phenomenon until now, von Andrian said.

He added that blood stem cells do not just give rise to cells that form the immune system, but that “they are part of the immune system.”

The study alters the perception that blood stem cells play a passive role in the immune system, according to David T. Scadden, co-director of the Harvard Stem Cell Institute.

“It might change people’s view on the purpose of blood stem cells’ circulation,” Scadden said. “It might influence what is taught in classrooms about blood stem cells’ role.”

Assistant Professor of Pathology Amy J. Wagers, co-author of the new study, said the group’s research answered the question of why blood stem cells would want to visit the tissues in the first place.

“We discovered that one reason for the blood stem cells to circulate to the tissues would be to produce immune cells,” she said, adding that this finding might lead to applications in clinical transplantation.

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