Detection of immunoglobulin G antibodies in melanoma sera reactive with intracellular proteins.

Immunoglobulin G (IgG) antibodies reactive with intracellular components of transformed cells were detected in 26/35 sera from patients with melanoma using immunofluorescence and/or Western blotting. By extracting cellular proteins with either sodium dodecyl sulphate or moderate concentrations of salt (400 mM NaCl), the protein antigens were partially characterized by immunoblotting procedures. Although considerable heterogeneity in the molecular weights of the protein antigens was observed, two common groups were delineated. The anti-Pol antibodies reacted with 30 kd cytoplasmic protein and the anti-Ca antibodies recognized acidic high molecular weight (75-95 kd) proteins. These antigens were detected in all transformed cell lines tested, but were not restricted to them. Anti-Ca and anti-Pol antibodies were not found in sera from patients with other solid tumors or in systemic lupus erythematosus.