Rat monoclonal antibodies to the external domain of the product of the C‐ erb B‐2 proto‐oncogene

With the breast carcinoma cell line BT 474 used as a source of antigen, four rat monoclonal antibodies (MAbs) (3 lgG 2a and I IgA) have been prepared against the external domain of the product of the c‐erb B‐2 proto‐oncogene. All 4 antibodies stain frozen sections of tissues that over‐express the product of the c‐erb B‐2 proto‐oncogene, and competitive binding assays showed that the antibodies recognized 2 non‐overlapping epitopes. Representative antibodies from the two groups (ICR12 and 13) were shown to specifically immunoprecipitate a 190kDa protein from 35 S‐methionine‐labelled breast carcinoma cells where the c‐erb B‐2 is amplified (BT 474 and MDA‐MB 361). Two of the antibodies (ICR12 and ICR17) bind to the denatured antigen in Western blots and ICR 12 stains formolsaline‐fixed sections of breast carcinoma tissue that overexpresses the product of the c‐erb B‐2 proto‐oncogene. These antibodies should be useful not only for immunocytochemical diagnoses but also for radio‐immunoscintigraphic and therapeutic applications.