IMMUNOPRECIPITATION OF MELANOGENIC ENZYME AUTOANTIGENS WITH VITILIGO SERA - EVIDENCE FOR CROSS-REACTIVE AUTOANTIBODIES TO TYROSINASE AND TYROSINASE-RELATED PROTEIN-2 (TRP-2)

In the present study we describe the detection of TRP-2 antibodies in vitiligo patients using in vitro S-35-labelled human TRP-2 in a radioi mmunoassay. Of 53 vitiligo sera examined in the assay, three (5.9%) we re found to be positive for TRP-2 antibodies. In contrast, 20 control sera, sera from 10 patients with Hashimoto's thyroiditis and sera from 10 patients with Graves' disease were all negative. All three patient s positive for TRP-2 antibodies (mean age 54 years, age range 50-63 ye ars) had had vitiligo of the symmetrical type for more than 1 year and all of them also had an associated autoimmune disorder: Graves' disea se in one and autoimmune hypothyroidism in two. In addition, antibodie s to the melanogenic enzyme tyrosinase were present in their serum. To examine any immunological crossreactivity between TRP-2 and tyrosinas e, the three vitiligo sera positive for TRP-2 antibodies were preabsor bed with COS-7 cell extract containing either expressed TRP-2 or tyros inase, and subsequently used in the radioimmunoassay. These absorption studies indicated that preincubation with both proteins inhibited the immunoreactivity of the positive sera in the immunoassay using in vit ro translated S-35-TRP-2. This antibody cross-reactivity suggests the humoral response to the two melanogenic enzymes in these patients may not be entirely independent.