CELL-MEDIATED-IMMUNITY IN AN AGING POPULATION

Abstract

Patients (880) hospitalized in a geriatric hospital were routinely tested with 2, 10, 30 and 100 IU of tuberculin. Among those, 54 patients were selected on the basis of negative skin tests and absence of evidenct disease interfering with the function of the immune apparatus. A battery of tests for cell-mediated immunity was applied to those 54 patients. Elderly patients having a negative test to 100 IU tuberculin show very infrequent sensitization to 3 other thymus-dependent antigens. The capacity of this selected population to become sensitized to DNCB [dinitrochlorobenzene] is poor (20%). They exhibit a low per cent of peripheral blood T [thymus-derived] cells (36%) and a poor capacity to respond in vitro to mitogens such as PHA [phytohemagglutinin]. Testing the in vitro response to a battery of antigens demonstrated a good correlation with the results of the skin tests. The leukocytes of 25% of this selected population failed to produce LIF [lymphocyte inhibitory factor] in vitro in the presence of PHA. These results suggest not only an absolute decrease in the population of circulating T lymphocytes.