Tumor-reactive human immunoglobulin G monoclonal antibody from a melanoma patient.

To study tumor-associated antigens that are immunogenic to humans, we have generated human monoclonal antibodies by fusing lymph node lymphocytes of a melanoma patient with a mouse myeloma cell line. We examined in detail the reactivity of one IgG antibody, termed 2-139-1. Immunostaining was performed with purified antibody conjugated to biotin. Binding was visualized by the avidin-biotin-peroxidase complex. With cultured cells, 2-139-1 stained 12 of 12 melanomas and 12 of 16 carcinomas. Reactivity was not detectable in seven neural crest tumors, six sarcomas, and 45 lymphomas and leukemias. This spectrum of reactivity was confirmed with sections of human tissues. The human monoclonal antibody 2-139-1 reacted against melanomas and not banal nevi. While the antibody reacted strongly to adenocarcinomas of the colon, prostate, rectum, and pancreas, it did not stain all the carcinomas tested. Furthermore, reactivity was not seen against sarcomas. Interestingly, 2-139-1 did not bind to the majority of the cells in normal tissues, including fetal tissues. The reactivity of 2-139-1 may be representative of the humoral immune response found in the regional lymph nodes of cancer patients. The distribution of this epitope in various tumors was fairly limited and appeared to be associated with malignant transformation.