Immunohistochemical study of types I, III and IV collagen in fibrosis of diseased gingiva during chronic periodontitis: A light and electron microscopic study

The distribution of type I, III and IV collagen and their ultrastructural organization have been studied in fibrotic gingival connective tissue of patients with longstanding cases of chronic periodontitis. The use of an immunofluorescent procedure has shown that the diseased connective tissue was made up of both type I and type III collagen. Type I collagen was strongly fluorescent and appeared to be the main gingival collagenous component, equally distributed in all layers of the tissue, whereas type III collagen was weakly fluorescent and mostly found in gingival papillae, but not around blood vessels. Standard electron microscopy and immunolabelling using the peroxidase procedure have shown that the large and dense bundles of type I collagen of P 1 , which is the main pattern of organization of the gingival connective tissue, were infiltrated by small bundles of microfilaments (10–15 nm) identified as the fibrillar form of type III collagen. However, in P II , the second pattern of organization of the gingival connective tissue, type I collagen fibers were predominant and gave a fibrous feature to this area. Type IV collagen was exclusively located in the thickened, degraded Lamina densa of basement membranes.