An immunohistochemical study of collagens in trachoma and vernal keratoconjunctivitis

Purpose To analyse the distribution and types of collagen in the conjunctiv a of patients with trachoma and vernal keratoconjunctivitis (VKC). Methods Conjunctival biopsy specimens were collected from 9 patients with a ctive trachoma, 9 patients with scarred trachoma, 6 patients with active VK C and 9 control subjects. The presence and distribution of collagen was ass essed microscopically with immunohistochemical techniques and a panel of mo noclonal and polyclonal antibodies directed against types I, III, IV and V collagen. Results In normal conjunctiva, the staining for types I and III collagen wa s localised to the substantia propria. Type IV collagen was located in the epithelial, vascular endothelial and accessory lacrimal gland basement memb ranes. Staining for type V collagen was absent. New type V collagen deposit ion close to basement membranes was noted in active trachoma, scarred trach oma and VKC, The extent of deposition of type V collagen was markedly incre ased in scarred trachoma when compared with active trachoma. Staining for t ype IV collagen showed irregularly thickened epithelial basement membrane i n active trachoma, and a marked increase in basement membrane type IV colla gen was noted in scarred trachoma. Immunoreactivity of types I and III coll agen increased in active trachoma and decreased in scarred trachoma. VKC co njunctiva contained increased amounts of types I,III and IV collagen due to marked increase in the thickness of vascular endothelial basement membrane and very prominent deposition of types I and III collagen around stromal v essels. Conclusions Our data indicate new type V collagen formation in the conjunct iva from patients with active trachoma, scarred trachoma and VKC. Increased deposition of types I,III and IV collagen is noted in VKC and active trach oma. Our findings suggest that increased deposition of type IV collagen and new type V collagen formation contributes to the development of conjunctiv al fibrosis in scarred trachoma.