The diagnostic application of specific anti-procollagen sera: I. Analysis of skin biopsies

Abstract

Antisera were prepared in rabbits against mature calf skin collagen (type I) and a polypeptide characteristic for calf skin procollagen (type I). The latter peptide is attached to the aminoterminal end of the α-chains and cleaved off during normal maturation by a specific enzyme, procollagen peptidase. For the present study procollagen was isolated from the skin of calves with an inborn deficiency of procollagen peptidase, a disease called dermatosparaxis. The antisera to mature collagen and procollagen were rendered specific by appropriate immunoadsorption procedures. These sera show a strong cross-reaction with human skin collagen and procollagen. While anti-collagen sera produced indirect immunofluorescent staining of the whole dermis, anti-procollagen sera only react with the uppermost dermal layer (stratum papillare) of unfixed frozen sections of normal human skin biopsies. Frozen unfixed sections of skin biopsies from 50 patients with various diseases were analyzed in indirect immunofluorescence tests with anti-procollagen sera. In 19 cases, material from uninvolved skin areas were also available for study. Skin from patients with “collagen diseases” (systematic lupus erythematosus, dermatomyositis, scleroderma) reacts like normal skin. Skin from patients with psoriasis vulgaris and lichen planus shows broad subepithelial zones of procollagen fluorescence. Keloids display very weak or no procollagen immunofluorescence in several instances. In three studied cases with prolonged local corticoid treatment a normal procollagen immunofluorescence pattern reappeared. Biopsies from one case of Wilson's disease under prolonged d-penicillamine therapy and one case of epidermolysis bullosa also lacked reactivity with anti-procollagen sera. Uninvolved skin of all patients revealed normal procollagen immunofluorescence. It is concluded that immunofluorescence studies with specific antisera to procollagen provide a simple and exact tool for the localized analysis of collagen metabolism.