Front-line Immune Cells Mature In Four Stages, Study Shows

... Researchers here have cracked the site and the stages of development for the last major set of human immune cells. 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. ...