Immune-complexes in malignant skin melanoma: quantitation by three methods, purification, and characterization of their non-tumor related constituents.

Circulating immune-complexes (ICs) and complement system (C) were studied in sera from 10 patients with malignant skin melanoma. The presence of ICs was demonstrated in all of them by three distinct methods. Moreover, ICs were purified in all the patient sera. The fact that ICs were detected in each serum and that the results of the analysis obtained by the different methods were not overlapping is discussed. It is stressed that the differences among the intrinsic characteristic of each technique are responsible for these discrepancies. The C profile was altered if compared with normal values, but it was not strictly characteristic for an ICs disease. In the purified ICs C3, C4, IgM, IgC1, and IgG3 were demonstrated; C1q, C1s, IgA, IgG2, and IgG4 never. It is noteworthy that a rheumatoid activity was found in the purified material and that this activity was significantly correlated with serum immuno-conglutinins (IKs) titre.