Antibody response against the c-erbB-2 oncoprotein in breast carcinoma patients

Indirect immunofluorescence analysis of sera from breast carcinoma patients whose tumors were characterized for overexpression of the c-erbB-2 oncoprotein (p185HER2) and for lympho-plasma cell infiltration, revealed no circulating antibodies specifically directed against the p185HER2 molecule in the 20 samples tested, whereas supernatants of B-cell clones, derived from Epstein-Barr virus-transformed peripheral blood lymphocytes from 10 of these patients, contained such antibodies in 6 of the 7 c-erbB-2- and lympho-plasma cell infiltration-positive cases. The antibodies contained in two of the positive supernatants immunoprecipitated a M(r) 185,000 molecule from oncoprotein-positive cell extracts that was identified as the oncoprotein in sequential immunoprecipitation experiments with anti-p185HER2 monoclonal antibodies. No cells producing antibodies with a similar reactivity were obtained from Epstein-Barr virus-transformed peripheral blood lymphocytes from breast carcinoma patients with p185HER2-negative tumors or from healthy donors. These data prove the existence of an antibody response specifically directed against the p185HER2 oncoprotein in breast carcinoma patients that may represent an important effector mechanism in the control of c-erbB-2-overexpressing tumors.