The relationship between the keratocyst antigen (KCA) and keratin

The relationship of the keratocyst antigen (KCA), the soluble component present in most keratocyst fluids, and keratin, was studied with immunofluorescence microscopy comparing their distribution in developing mouse embryonic teeth and in human ameloblastomas. In these tissues both molecules showed a strong codistribution in epithelial cells. In the embryonic teeth both molecules were present in the stratum intermedium cells between the stellate reticulum cells and ameloblasts, but the secretory ends of the ameloblasts showed fluorescent staining only for keratin. The relationship was further investigated by comparing the physicochemical characteristics of KCA and keratin. Results on immunoblotting and two-dimensional gel electrophoresis showed that KCA existed in keratocyst fluid as a 60-68,000 dalton polypeptide with an isoelectric point of pI 6.8. Immunoblotting analysis of various isolated keratins revealed a typical polypeptide pattern of each keratin when anti-KCA antiserum was used for staining. These findings suggest that KCA and keratin are related molecules and that KCA may be a soluble component of keratin.