Immunologic response in an elderly population with a mean age of 85.

Previous studies of changes in immune responses in the elderly have been limited in both number and age of elderly subjects and have produced conflicting results. Using 260 subjects, mean age 84.6, the present study conclusively demonstrates that T cell response is decreased in the elderly. Decreases in response to phytohemagglutinin and concanavalin A were demonstrated in groups aged 70 to 79, 80 to 84, and 85 to 89, although a group 90 to 106 years old showed a decreased response only to phytohemagglutinin. None of the groups had a decreased response to pokeweed mitogen. No response to all three mitogens was observed in 13 percent of the group aged 70 to 89, but in none of the group aged 90 to 106 or in the young groups. No differences in natural killer cell cytotoxicity were observed among the elderly groups. In contrast to previous studies, these results suggest that: the decreased immune response of the elderly is not directly related to age, over age 70; and there may be a selection process in which subjects who live to the age of 90 are those in whom the least decrease in immune response is demonstrated.