Plaque-forming cell response of human blood lymphocytes. III. Cellular basis of the reduced immune response in the elderly.

Overview

The cellular basis for the reduced immune response of the elderly was studied in vitro. It was found that, with respect to the capacity to respond to relatively T-independent B cell activators by proliferation and generation of plaque-forming cells (PFC), the purified B cell population of aged subjects is relatively intact. Furthermore, macrophages from old and young subjects produce T cell-replacing factors in equivalent amounts. The depressed proliferation and PFC responses to B cell activators in unfractionated lymphocytes from the elderly thus appear to be due to suppressor activity present in a surface Ig-negative cell population, suggesting that alterations in the regulatory (helper and suppressor) functions of T cell populations are the major cause of the reduced humoral immune response associated with aging.