MORPHOLOGICA L STUDY OF MOUSE (BALB/c) THYMUS A FTER HIGH A ND LOW DOSE DEXA METHA SONE TREATMENT

Dexamethasone induces thymic atrophy and thymocyte apoptosis. In the present study histological and ultrastructural changes which occur in the thymus of the mouse (BALB/c) following treatment with high (20 mg/kg) and low (8 mg/kg) doses of dexamethasone were investigated. In low dose treated mice, apoptotic cells were observed focally and localized mainly in thymic nurse cells (T.N.C.). A zone of intact thymocytes was formed in the medulla of animals receiving 20 mg/kg of dexamethasone as well as an increase in trans-endothelial vesicles and a decrease in the size of the vesicles in the cortical capillaries. The enveloped thymocytes within thymic nurse cells respond to dexamethasone through apoptosis, and these changes were seen to be more severe in mice treated with high doses of dexamethasone. The formation of apoptotic cells in the thymus caused by low dose dexamethasone mimics the physiological process of cell death. Differential effects of low dose and high dose dexamethasone may have pharmacological and immunological implications.