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Setting the stage for infection.

Setting the stage for infection

Healthy people who show persistent deficiencies in the activity of natural killer (NK) cells -- a type of immune cell believed to play a role in the body's initial defense against infection and malignancy--run an increased risk of developing colds, flu and other infections, according to a preliminary study directed by psychologist Sandra M. Levy of the University of Pittsburgh School of Medicine. In young adults who perceive their daily hassles and stress as intense, lowered response rates of NK cells are strongly linked to the contraction of infectious disease, Levy says.

She and her co-workers recruited 106 healthy volunteers between the ages of 18 and 45 from the Pittsburgh area. The sample was predominantly white and college-educated. For six months, the researchers regularly measured NK activity (the ability of NK cells to destroy target cells in a standard laboratory analysis) and numbers of NK and other immune cells. At least once a month, they also gathered participants' self-reports of stressful incidents and their severity.

About one-third of the volunteers had NK activity below the population average throughout the study. NK activity was usually within the normal range, however, and NK cell counts were normal. Participants with low NK activity reported substantially more infection-related illness during the study, including colds, influenza, pneumonia, cold sores, gastrointestinal illnesses, fever and sore throat. The most cases of infectious illness occurred among volunteers with low NK activity who were younger than 29 and reported intense responses to stressful events.

The cause of consistently low NK activity remains unknown, Levy says, but the study results suggest physicians might screen young adults in stressful situations -- such as military duty or medical school -- for immune patterns and ask them about their perceptions of daily stress. Evidence indicates that marked increases in NK activity can result from relaxation training combined with counseling focused on dealing effectively with stress, Levy notes.
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Title Annotation:natural killer cells
Author:Bower, Bruce
Publication:Science News
Date:Aug 26, 1989
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