Localization and quantification of alpha-1-proteinase inhibitor in the human cornea

alpha-1-Proteinase inhibitor, formerly called alpha-1-antitrypsin, was detected in human corneal epithelium, stroma, Descemet's membrane and endothelium using an indirect immunolocalization technique. The average alpha-1-proteinase inhibitor levels detected by an immunodot blot assay in the epithelium, stroma and Descemet's membrane-endothelium extracts per total human cornea were 29.5 micrograms, 54.3 micrograms and 3.5 micrograms, respectively. Immunolocalization on Western blots of SDS polyacrylamide electrophoresis gels revealed that all three layers contained a molecule with a molecular weight equal to the native alpha-1-proteinase inhibitor. Additionally, in the epithelial and stromal extracts minor bands at 75 kD and 110 kD were noted which are possibly due to complexes with proteases. The 110 kD band alternatively may be a dimer of the inhibitor. The epithelial extract contained bands at 40 kd and less than 30 kD indicating the presence of proteolysis products. alpha-1-Proteinase inhibitor probably plays a major role in the protection of the cornea from proteases released by inflammatory cells.