AUTOIMMUNITY TO A CORNEA-ASSOCIATED STROMAL ANTIGEN IN PATIENTS WITH MOORENS ULCER

Purpose. To purify and characterize a cornea-associated antigen (CO-ag ) and to determine antibody levels to CO-Ag in patients with Mooren's ulcer. Method. Standard ion exchange and gel filtration chromatographi es were used to isolate and purify CO-Ag from crude bovine stromal ext racts. The serum of a patient with Mooren's ulcer, containing a high l evel of antibodies directed against CO-Ag, was used to monitor isolati on procedures. Using this newly purified CO-Ag, an enzyme-linked immun oabsorbent assay was used to detect the presence of antibodies to CO-A g in the sera of other patients with Mooren's ulcer. Results. CO-Ag wa s purified to apparent homogeneity from bovine corneal stromal extract s by a series of ion exchange chromatographies and gel filtration. Pol yacrylamide gel electrophoresis showed that CO-Ag was a tetramer with a molecular weight of 30,000 d that may dissociate under denaturing co nditions into a monomer of 7000 d. Strong indirect immunofluorescent s taining was demonstrated of the stroma by guinea pig anti-CO-Ag antibo dy. A statistically significant difference in the level of specific an tibodies to CO-Ag between patients with Mooren's ulcer and controls wa s found (P < 0.001). The antibody level was elevated in patients with Mooren's ulcer (mean antibody level, 0.58 +/- 0.13) compared with the controls (mean antibody level, 0.22 +/- 0.04). Conclusion. These resul ts suggest that an autoantigen exists in the corneal stroma that react s with serum antibodies from patients with Mooren's ulcer. The availab ility of a purified corneal antigen could facilitate the diagnosis and define the pathogenetic mechanisms in Mooren's ulcer.