Identification of two different surface epitopes of human ovarian epithelial carcinomas by monoclonal antibodies

Monoclonal antibodies (Mabs) against human ovarian mucinous and serous carcinoma were obtained by the Mab technique. Their reactivities against human tumors were tested by indirect immunofluorescence. One of the Mabs, named 4C7, derived from the spleen cells of mice immunized with mucinous carcinoma line OVA-1, reacted to ovarian mucinous carcinoma, endometrioid carcinoma, and mesonephroid carcinoma but did not react to ovarian serous carcinoma. Another Mab, 3C2, obtained from the spleen cells of mice immunized with serous carcinoma line HOC-21, reacted to serous carcinoma and endometrioid carcinoma of ovary, but never reacted to mucinous carcinoma or mesonephroid carcinoma. Neither of the Mabs reacted to other types of ovarian carcinomas such as undifferentiated carcinoma, dysgerminoma, endodermal sinus tumor, and malignant teratoma of ovary, and also did not react to any benign ovarian tumors or other normal human tissues. Both Mabs 3C2 and 4C7 had no reactivity to carcinoma of other organs such as stomach, colon, lung, lymphoid system, and kidney and also did not react to human lymphocytic or carcinoembryonic antigen as confirmed by using many human cell lines and surgically resected samples. Since the cross-reactivities of these Mabs were limited within the ovarian epithelial carcinomas, it is suggested that two distinct epitopes are expressed on the ovarian epithelial carcinomas. One epitope, identified by Mab 4C7, is expressed only on mucinous carcinoma, endometrioid carcinoma, and mesonephroid carcinoma, while the epitope, identified by Mab 3C2, appears only on serous and endometrioid carcinoma.