Stress, Coping, and Infectious Illness: Persistently Low Natural Killer Cell Activity as a Host Risk Factor

Persistently Low Natural Killer Cell Activity and Circulating Levels of Plasma Beta Endorphin: Risk Factors for Infectious Disease

“…We stratified by mean age and pattern of NK activity because previous research (10,23) has shown that the pattern of NK activity profiles, rather than simple mean NK activity, has potentially important health relevance, and that a persistently low NK pattern is found more frequently in chronologically younger individuals.…”