APOLIPOPROTEIN-A-I AND B-DISTRIBUTION IN THE HUMAN CORNEA

Purpose. To determine the presence and localization of apolipoprotein A-I, a marker for high density lipoprotein, and apolipoprotein B, a ma rker for low density lipoprotein, in human cornea; to examine the rela tionship of these lipoprotein markers with areas of lipid accumulation in the cornea. Methods. A-I and B apolipoproteins were localized in f rozen sections of human corneas with specific monoclonal antibodies us ing avidin-biotin immunoperoxidase labelling. Corneal lipid was coloca lized with apolipoproteins by oil red 0 staining of immunostained sect ions. Results. Staining data showed that apolipoprotein B and lipid ac cumulated in the extracellular spaces of peripheral corneal stroma. Ho wever, their distributions were not coincident. The posterior region o f peripheral corneal stroma (including Descemet's membrane) often cont ained lipid without immunodetectable apolipoprotein B. Unexpectedly, a polipoprotein A-I was associated with many keratocytes throughout the cornea in addition to an extracellular distribution heaviest in periph eral cornea. Conclusions. Lipid deposits lacking apolipoprotein B in p eripheral cornea suggest that if accumulated corneal arcus lipid is de rived from extracellular deposition of plasma low density lipoprotein, the low density lipoprotein is altered such that it looses its immuno reactive apolipoprotein B. The unexpected association of apolipoprotei n A-I with keratocytes suggests that these cells are either taking up or synthesizing a protein sharing an immunoreactive epitope with apoli poprotein A-I.