ENZYME HISTOCHEMICAL STUDY ON HUMAN THYMUS AND ITS AGE CHANGE

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Abstract
Human thymuses, ranging in age from newborn-62 yr old, were studied enzyme histochemically. Thymic epithelial cells covering cortical surface and bordering vascular areas in the medulla were positive for 5''-nucleotidase, but not for other enzymes. The thymic epithelial cells composing Hassall''s corpuscles were positive for acid phosphatase, esterases, .beta.-glucuronidase and alkaline phosphatase, regardless of age, but totally negative for 5''-nucleotidase and ATPase. All enzymes examined except for .beta.-glucuronidase were demonstrated in some of the thymic epithelial cells scattered in the medulla, although the pattern of distribution and the degree of positivity were different by enzymes. The thymic epithelial cells are apparently composed of functionally heterogenous subpopulations. Acid phosphatase was demonstrated in thymocytes in both cortex and medulla, but 5''-nucleotidase and ATPase were observed in some thymocytes in the medulla of young thymus.