ANTIBODY-RESPONSE AGAINST THE C-ERBB-2 ONCOPROTEIN IN BREAST-CARCINOMA PATIENTS

Indirect immunofluorescence analysis of sera from breast carcinoma pat ients whose tumors were characterized for overexpression of the c-erbB -2 oncoprotein (p185HER2) and for lympho-plasma cell infiltration, rev ealed no circulating antibodies specifically directed against the p185 HER2 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 immunopr ecipitated a M(r) 185,000 molecule from oncoprotein-positive cell extr acts that was identified as the oncoprotein in sequential immunoprecip itation experiments with anti-p185HER2 monoclonal antibodies. No cells producing antibodies with a similar reactivity were obtained from Eps tein-Barr virus-transformed peripheral blood lymphocytes from breast c arcinoma 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.