Specific immunohistochemical localization of type III collagen in porcine periodontal tissues using the peroxidase-antiperoxidase method.

Specific antibodies to porcine gingival type III collagen were raised in sheep. After purification on collagen affinity columns the antibodies were used for immunohistochemical localization of type III collagen in porcine periodontal and dental tissues employing the peroxidase-antiperoxidase (PAP) procedure. The extent of staining of the periodontal tissues was found to approximate the amount of type III collagen measured biochemically. A fairly uniform distribution of type III collagen was observed in the periodontal ligament and gingiva with more intense staining often being associated with blood vessels. A regular pattern of weakly staining fibers could be demonstrated throughout the cementum and in parts of the alveolar bone tissue. In addition, occasional sites in the cementum having a different morphological appearance from the rest of the cementum exhibited bundles of positively stained fibers. Although the bone tissue was essentially unstained, fibers in the endosteal spaces stained strongly. Sharpey's fibers passing from the soft connective tissues into alveolar bone and cementum also stained strongly. Three distinct arrangements of collagen fibers stained by the type III collagen antibodies could be identified: first, a reticular pattern, which was seen at the junction of the gingival epithelium and connective tissue, and in the endosteal spaces and dental pulp; second, a more diffuse pattern of fibers intermingled with type I collagen in the soft connective tissues; and third, a coating of some Sharpey's fibers, having a core believed to be type I collagen, and of fibers in the cementum inclusions.