Two novel monoclonal antibodies reactive with different components of the rat thymic epithelium.

Two novel monoclonal antibodies (mAbs) (PT10B7 and PT13D11) have been raised against molecules of rat thymic epithelial cells (TEC). Streptavidin-biotin immunoperoxidase staining and double immunofluorescence using these mAbs and anti-cytokeratin (CK) antibodies showed that PT10B7 and PT13D11 mAbs bound to different components of rat TEC. PT10B7 mAb reacted with cortical and a subset of medullary TEC, whereas PT13D11 mAb labeled subcapsular/perivascular and most medullary TEC, including TE-R 2.5 TEC line of medullary origin. Their staining patterns were different from those seen using mAbs to CK10, CK18 and CK19 polypeptides and other anti-rat TEC mAbs produced so far. The differences in immunoreactivity of these two mAbs on rat thymus during ontogeny and on other epithelial cells of adult rats were also seen. Namely, PT13D11 stained ectoderm-derived epithelia, whereas PT10B7 stained some cells of simple epithelia. Cumulatively, these results reveal a fine phenotypic heterogeneity within rat thymic epithelium.