In vivo evaluation of age-associated changes in delayed-type hypersensitivity.

The effectiveness of a recently developed isotopic in vivo assay for the measurement of delayed-type hypersensitivity (DTH) was compared to that of the conventional skin sensitization assay based on the ear-swelling index. DTH was measured in young and old C57BL/6 mice under conditions of normal health, spontaneous reticular cell sarcoma, Sendai virus infections and under the above conditions, while being treated with a potential immunorestorative agent, mercaptoethanol. A good correlation was observed between the two types of assay. However the reliability and sensitivity of the isotopic assay was found to be superior to the conventional skin sensitization assay. Thus, under optimum conditions, the swelling assay showed a 35% decline in DTH in old mice, and the isotopic assay a 62% decline.