The clinical significance of antityrosinase antibodies in melanoma and related hypopigmentary lesions.

Abstract

Antityrosinase antibody is a newly detected antibody in the sera of patients with melanoma or vitiligo. The serum level of the antibody is measured by enzyme-linked immunosorbent assay (ELISA). The autoantigen is tyrosinase itself, the enzyme that participates in pigment (melanin) formation by both melanocytes and melanoma cells Antityrosinase IgG antibodies were found to be present in high titers in sera of patients with vitiligo in comparison to patients with melanoma or healthy volunteers. The level of antityrosinase antibodies in patients with metastatic melanoma was significantly higher than the level in healthy subjects, but insignificantly higher than the level in patients with no evidence of disease. Patients with melanoma and MAH (melanoma-associated hypopigmentation; vitiligo-like) had the same level of antityrosinase antibodies as the controls or the patients with metastatic melanoma. This observation reflected the possible absorption of antityrosinase antibodies by melanoma antigens, and pointed to the participation of the antibodies in the destruction of normal melanocytes in patients with melanoma, as part of the immune reaction towards this disease. The most interesting observation was the high level of antityrosinase antibodies in patients with vitiligo in comparison with the low level in patients with melanoma, patients with MAH, and patients with NED. Although the cutaneous manifestations of vitiligo and MAH are similar and result from destruction of melanocytes by specific antibodies, the two situations are immunologically different. The serum level of free antityrosinase antibodies could not serve as marker for the state of the disease or disease progression or relapse, as no significant difference could be detected between the levels in patients without evidence of disease to those with metastatic melanoma; nor could the levels of antityrosinase antibodies differentiate between the different sites of the primary lesion. However, we have shown that antityrosinase antibodies could be used for monitoring the response to active specific immunotherapy by injection of anti-idiotypic antibodies mimicking the HMW-MAA. In the future, antityrosinase antibodies may be incorporated into immunotherapy for malignant melanoma.