Electron-immunocytochemistry of laminin and type-IV collagen in the junctional epithelium of rat molar gingiva

The present study was carried out to examine the ultrastructural localization of laminin and type-IV collagen in the junctional epithelium of rat molar gingiva by means of the indirect immunoperoxidase method. Intense laminin reaction occurred in both the internal and the external basal laminae. Laminin reaction products were observed within the cisternae of the rough endoplasmic reticulum of junctional epithelium cells and in concavities formed at the distal plasma membranes adjacent to the basal lamina. Small spherical bodies occurring in the concavities also reacted positively to laminin. Type-IV collagen reaction was intense in the external basal lamina. The internal basal lamina, however, showed no reaction for type-IV collagen. These results indicate that the internal basal lamina contains laminin but no type-IV collagen and that junctional epithelium cells seem very likely to be involved in the production of laminin.