Dermal architecture and collagen type distribution.

The human dermis consists of two morphologically different layers. A loose meshwork of thin collagenous fibres is characteristic for the adventitial dermis with includes the papillary and the periadnexal dermis. Thick, coarse collagen bundles are the main feature of the reticular dermis. Two different collagens, type I and type III occur in the dermis as shown previously by biochemical analyses. Antibodies specific for type I collagen or type III collagen and their corresponding precursors were used in indirect immunofluorescence tests to localize the various collagens in frozen sections of normal adult skin. Whereas type I collagen is found in all dermal layers, the main part of type III collagen can be found within the adventitial dermis. Antibodies against the precursor of type I collagen stain only a bandlike region immediately beneath the epidermis. Antibodies against the precursor of type III collagen stain the same regions as antibodies against the helical part of type III collagen.