IMMUNOHISTOCHEMICAL LIGHT AND ELECTRON-MICROSCOPY OF BASAL LAMINAR DEPOSIT

The formation of basal laminar deposit (BLD) is one of the histopathol ogic changes in the aging human macula. BLD is assumed to be an early stage of age-related macular degeneration. The location of BLD, betwee n the RPE plasma membrane and its basement membrane and in the outer c ollagenous zone of Bruch's membrane, and its ultrastructure suggest th at it is composed of excessive amounts of basement membrane material. The main components of basement membranes are type IV collagen, hepara n sulfate proteoglycans (HSPG) and laminin. Labeled antibodies against these components can therefore be used for the identification and loc alization of basement membrane material by means of immunohistochemica l techniques. In this study the presence of type IV collagen, laminin and HSPG was determined in aged human maculae by immunohistochemistry and immunoelectron microscopy. Tests for the presence of type VI colla gen and fibronectin were also performed. We obtained 76 eyes from 68 h uman subjects at autopsy or after surgical enucleation for anteriorly located choroidal melanomas. The finely granular component of BLD stai ned positive with antibodies against type IV collagen, HSPG and lamini n, but the long-spacing collagen component of BLD did not. Neither com ponent of BLD was stained with antibodies against type VI collagen or fibronectin. We conclude that BLD consists partly of excess basement m embrane material.