ACCESSORY FUNCTION AND PROPERTIES OF MONOCYTES FROM HEALTHY ELDERLY HUMANS FOR T-LYMPHOCYTE RESPONSES TO MITOGEN AND ANTIGEN

The waning of cell-mediated immunity during aging has been attributed primarily to defects in T lymphocyte properties and functions. We asse ssed the potential contribution of accessory dysfunction of monocytes from the elderly on responses of T cells to phytohemagglutinin (PHA) a nd to tetanus toxoid after in vivo boosting. Accessory function of mon ocytes from the elderly subjects for T lymphocyte responses to tetanus toxoid was comparable to the young. Expression of the cytokines inter leukin-1, interleukin-6 and tumor necrosis factor, the cell adhesion m olecules ICAM-1 and LFA-3 and the class II major histocompatibility mo lecule HLA-DR by monocytes from the elderly and young subjects was sim ilar. T lymphocytes from the elderly responded poorly to PHA. Monocyte s from the elderly had a decreased accessory function for PHA-stimulat ed T cells from young, third donors. Thus, although many accessory pro perties of monocytes from the elderly are normal, the monocyte and T l ymphocyte defects in the elderly for mitogen may represent interactive factors in cell-mediated immunity during aging.