Heterogeneity of rat thymic epithelium defined by monoclonal anti-keratin antibodies

Immunohistochemical characterization of rat TEC has been studied using a panel of monoclonal anti-keratin antibodies. These mAbs identified three distinct patterns of keratin subunit expression within thymic epithelium assessed by streptavidin-biotin immunoperoxidase staining and double immunofluorescence staining. K8 and KII mAbs labelled almost all epithelium, while K18 stained cortical epithelium and a subpopulation of medullary TEC. KI, K7 and K19 mAbs bound to the subcapsular/subtrabecular flat epithelial cell layer, TEC lining some perivascular spaces in the cortex, a subpopulation of medullary TEC and interstitial epithelial cystic structures. Double immunostaining revealed further heterogeneity of subunit keratin compositions in epithelial cells of particular thymic microenvironments suggesting their different origin or development stage.