โ Scribed by F. A. Salinas; L. H. Smith; J. W. Goodman
No coin nor oath required. For personal study only.
Although it is well known that thymus function changes with age, it is not known whether these changes are associated with specific thymocyte populations. Since one criterion of specificity is cell size, we studied the size distribution of thymocytes from mice 0.5 days to 30.5 months of age. Body weight, thymus weight, and thymocyte yield were also measured. The mean cell volume of thymocytes from 8.5 to 13 week old mice was 326 p3, with two detectable subpopulations. Mean thymocyte size was found to change with age. During the first postnatal week, the mean cell volume of the whole thymocyte population increased from 200 to 350 p s , and the percentage of large cells increased greatly and constituted 90% of the whole population a t four days or age. A rather slow decline i n mean cell volume with some fluctuation occurred throughout the remaining life span, and at 30.5 months the mean had dropped to about 190 p3. We suggest on the basis of these data that large thymocytes are involved i n the contribution of the thymus to early postnatal development of the immune system and that the age-related functional capacity of the thymus is related to the size of the thymocyte population.
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