POSSIBLE ROLE OF MONKEY GINGIVAL FIBROBLASTS IN EXTERNAL BASEMENT-MEMBRANE MAINTENANCE

Morphological and immunocytochemical investigations were made of the i nterface between the junctional epithelium and connective tissue in gi ngiva from young monkeys (Macaca fuscata), Some fibroblasts with consp icuous cytoplasmic organelles, including the elements of rough endopla smic reticulum, the Golgi apparatus, and mitochondria, were found clos e to the external basement membrane in the connective tissue underlyin g the junctional epithelium. Occasionally, cytoplasmic cell processes either made contact with the lamina densa of the basement membrane or came into direct contact with the plasma membrane of the basal layer o f junctional epithelium cells, Fragments of a structure like that of t he basement membrane were observed between the process and the basal c ells. Fibroblasts could be seen very close to the disrupted portion cr eated by the passage of leukocytes migrating into the junctional epith elium through the external basement membrane. Immunoperoxidase methods demonstrated a positive reaction product for laminin on the external basement membrane. This product was observed in the rough endoplasmic reticulum of junctional epithelium cells and of gingival connective ti ssue fibroblasts located close to the junctional epithelium basement m embrane. The cytoplasm of fibroblasts distant from the epithelium, how ever, demonstrated no immunoreactivity. These results suggest that, in cooperation with epithelial cells, some fibroblasts located near the junctional epithelium can produce such basement membrane components as laminin and that these components may serve to stabilize and/or resto re previously assembled basement membrane.