The researchers found that natural killer (NK) cells, one of the body's front-line defenses against cancer and infections, mature from progenitor stem cells in four discrete stages. They also found that this happens in secondary lymphoid tissue such as tonsils and lymph glands.

Key discoveries made decades ago in animals and humans showed that the other two major types of immune cells in the body, T cells and B cells, developed in the thymus and bone marrow, respectively. However, the site and stages of human NK cell development have eluded investigators until now.

The findings advance the understanding of NK cells, which play a key role in triggering broader immune responses such as the body's permanent protection following vaccination. Understanding the secrets of NK cell development in humans could lead to new therapies for cancer, infection and for patients with immune deficiencies.

The study by researchers at the Ohio State University Comprehensive Cancer Center (OSUCCC) is published in the April 17 issue of the Journal of Experimental Medicine. Identification of the stem cell from which the human NK cell is derived was published by the OSUCCC research team last year in the journal Immunity.

"While there is a lot more work to do, this discovery unlocks another of Mother Nature's secrets," says principal investigator Michael A. Caligiuri, director of the OSUCCC and the Division of Hematology-Oncology.

"Still, we believe it opens new doors to manipulating the human immune system to our benefit, and we're working on that right now," says Caligiuri, who is also professor of internal medicine, of molecular virology, immunology and medical genetics and of veterinary biosciences.

"The findings will also boost NK-cell research," says first author Aharon G. Freud, a physician wh
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Contact: Darrell E. Ward
Darrell.Ward@osumc.edu
614-293-3737
Ohio State University
19-Apr-2006