Quantitative changes in AKR thymocyte subsets preceding the onset of leukemia.

The evolution of T-cell subsets in the thymuses of leukemia-prone AKR mice and of non-leukemia-prone BALB/c mice was compared for a period of 9 months. In AKR mice there is a sharp rise in thymic hormone sensitive thymocytes bearing a high concentration of Thy 1 antigen. While these cells also rise with age in BALB/c mice, they do so more slowly. The response of thymocytes to Con A was also compared between the two strains: the response of AKR cells drops to below significant levels within seven months, while BALB/c cells remain reactive throughout the experimental period. Since these age-related changes in Thy 1 antigen density and Con A reactivity can be reversed after incubation with a thymic hormone preparation, it is concluded that they are the result of a decrease in thymic hormone secretion, that this decrease is much more pronounced in AKR mice than in BALb/c mice and may therefore play a role in the etiology of the AKR leukemia.