Influence of ageing on blastogenesis of mouse thymocytes in response to concanavalin A

The influence of ageing on the blastogenic response of mouse thymocytes to a mitogen was investigated. Thymocytes from mice of various ages (10-70 days) were incubated with the mitogen, concanavalin A, to induce blastogenesis. The thymocytes were then incubated with 3H]thymidine, and the radioactivity of 3H]thymidine taken up by the cells was measured. The stimulation index (ratio of radioactivity uptake by cells incubated with and without mitogen) was used as a measure of blastogenesis of thymocytes. The stimulation index of thymocytes from 10-day-old mice was 2.9; it increased with age, reaching a peak of 33.7 in 40-day-old mice and then gradually decreasing to 8.2 in 70-day-old mice. The blastogenesis of thymocytes, an indicator of thymus function, was thus found to change considerably with age.