AGE-RELATED-CHANGES IN LOCALIZATION OF THYMOSIN IN THE HUMAN THYMUS

Abstract

Using an indirect fluorescent antibody technique, localization of thymosin .alpha.1, thymosin .beta.3 and thymosin fraction 6 was studied in human thymus glands ranging in age from newborn to 62 yr old. Thymosin .alpha.1 was detected specifically in thymic epithelial cells of the medulla and in cells covering the cortical surface. Thymosin .beta.3 was detected almost exclusively in cells covering the cortical surface, Epithelial cells in the medulla, which were positive for thymosin .alpha.1, decreased in number progressively with age, beginning at around 13 yr of age. Epithelial cells positive for thymosin .alpha.1 and covering the cortical surface were observed in thymus tissue from all ages, although the absolute number decreased. Several of the peptide components of thymosin fraction 6 were found in thymic epithelial cells and in macrophages in the thymus and spleen. [Thymosin has been shown to be involved in certain immunologic functions.].