Hormonal function and proliferative activity of thymic cells in humans: immunocytochemical correlations.

OBJECTIVES The immunocytochemical study of the localization of hormones in thymic cells has been performed to clarify possible correlations of their expression with proliferative activity of thymocytes. METHODS We used commercial antibodies to serotonin, melatonin, somatostatin, glucagon, gastrin, beta-endorphin and histamine, and ABP or BSP kits for visualization of reaction. Computer image analysis was used to find correlations between hormone production and proliferative activity of thymocytes. RESULTS Different subpopulations of thymocytes are able to produce hormones: precursors of T-lymphocytes (CD4-CD8-) contain serotonin and melatonin, immature cortical cells (CD4+CD8+) produce only serotonin, mature medullar cells (CD4+CD8-) show immunoreactivity to serotonin, melatonin, beta-endorphin and histamine. The expression of serotonin, somatostatin and gastrin is localized in thymic epithelial cells, formatting Gassal's bodies. Proliferative activity of thymocytes depends from the expression of serotonin and somatostatin in thymic cells. CONCLUSION The data received testify the expression of different hormones in human thymic cells and showing by this fact high endocrine activity of thymus. The presence of correlations between hormonal expression and cell proliferative activity could be considered as the bright illustration of important role of neuroimmunoendocrine mechanisms in the regulation of local thymic homeostasis.