Human Malignant Melanoma: Assay of Tumor Associated Antigens by Use of Rabbit Antisera

The usefulness of rabbit antisera for the characterization of tumor associated antigens of human melanoma was studied.Membranes of human melanoma tissue were extracted by 2M potassium iodide and sonication. Antisera were raised in rabbits against these extracts as well as against melanoma membranes and cultured melanoma cells. Antisera were absorbed with normal human material.Two of 14 absorbed antisera were specific for tumor associated antigens: they reacted with melanoma extracts (counterimmunoelectrophoresis) and melanoma cells (immune adherence) but not with 20 extracts of normal tissue, erythrocytes, lymphocytes, bacteria and molds (counterimmunoelectrophoresis), not with human fibroblasts (immune adherence), not with human erythrocytes with known blood group antigens (hemagglutination) and normal human skin (immunofluorescence). Rabbit antisera did not contain antibodies against carcinoembryonic antigen and alpha-i fetoprotein (radioimmunoassay). Reactivity with tumor associated antigens could be directly demonstrated by two-dimensional immunoelectrophoresis.Two types of melanoma associated antigens could be discriminated: the first type with restricted specificity could be demonstrated by an antiserum that reacted with the extract used to raise it and in addition had a weak reactivity with 1 of 7 other extracts. Broader cross reactivity is characteristic for the second type: the corresponding antiserum reacted with 6 of 8 melanoma extracts