CuZn-superoxide dismutase in human thymus: immunocytochemical localisation and secretion in thymus-derived epithelial and fibroblast cell lines.

CuZn-superoxide dismutase (SOD) plays a key role in mediating the cellular response to oxidative stress. Its expression in normal thymus was investigated by immunohistochemical techniques and CD3-, CD68- and cytokeratin-specific staining, in order to identify thymocytes, macrophages and epithelial components. Immunocytochemical studies showed an overall CuZn-SOD thymic distribution with a prevailing concentration within thymic medulla. The analysis of CuZn-SOD release by thymus-derived epithelial and fibroblast cell lines showed the ability of both cell lines to release the anti-oxidant enzyme, especially in the presence of stress conditions as represented by serum and nutrient deprivation. These data suggest that CuZn-SOD could be a relevant antioxidant paracrine molecule in human thymus.