AUTOANTIBODIES TO EVOLUTIONARILY CONSERVED EPITOPES OF ENOLASE IN A PATIENT WITH DISCOID LUPUS-ERYTHEMATOSUS

Although the pathology of discoid lupus erythematosus is well document ed the causative agents are not known. Here, we report the identity of the target antigen of an autoantibody present in high titre in the se rum of a patient with discoid lupus erythematosus. We have demonstrate d that the antigen is enolase; first, because it has properties consis tent with this glycolytic enzyme (47000 MW, cytosolic localization and ubiquitous tissue distribution). Secondly, limited amino acid sequenc e determination after trypsin digestion shows identity with alpha-enol ase. Finally, the autoimmune serum immunoblots rabbit and yeast enolas e and predominantly one isoelectric form of enolase (pI similar to 6.1 ). These results indicate that the reactive autoepitopes are highly co nserved from man to yeast. The results also suggest that the autoantib odies are most reactive to the cr-isoform of enolase, although it is p ossible that they may also be reactive with gamma-enolase, and have le ast reactivity to p-enolase. The anti-enolase autoantibodies belong to the immunoglobulin G(1) (IgG(1)) isotype. This is the first report of IgG(1) autoantibodies to evolutionarily conserved autoepitopes of eno lase in the serum of a patient with discoid lupus erythematosus. Previ ous reports of autoantibodies to enolase have suggested associations w ith autoimmune polyglandular syndrome type I and cancer-associated ret inopathy. This report and an earlier report of what is likely to be en olase autoantibodies in two patients without systemic disease suggest that enolase autoantibodies have a broad association and are not restr icted to any particular disease.