Abstract
Natural killer (NK) cells have been thought to play a primary role in preventing neoplasia from the development. Because of the increase with age in the incidence of neoplasia, one can expect impaired NK activity in aged humans. To test this hypothesis, NK activity from young and old persons has been measured. Increase in NK activity was demonstrated in groups aged 71 to 75, 76 to 80 and 81 to 85, although groups of 65 to 70 years and more than 86 years showed a comparable NK activity to that in young persons (18 to 50 years). The difference in observed NK activity could not be attributed to differences in percentage of NK cells in the blood from old and young persons. Increase with age in the NK activity may make up the decline of immunologic competence with age for maintaining normal immune system homeostasis.
