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With the breast carcinoma cell line BT 474 used as a source of antigen, four rat monoclonal antibodies (MAbs) (3 IgG2a and I IgA) have been prepared against the external domain of the product of the c-erbB-2 proto-oncogene. All 4 antibodies stain frozen sections of tissues that over-express the product of the c-erbB-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 190 kDa protein from 35S-methionine-labelled breast carcinoma cells where the c-erbB-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 ICR12 stains formolsaline-fixed sections of breast carcinoma tissue that over-expresses the product of the c-erbB-2 proto-oncogene. These antibodies should be useful not only for immunocytochemical diagnoses but also for radio-immunoscintigraphic and therapeutic applications.

In pooled bile, obtained by cannulating the common bile duct of normal rats, the immunoglobulins were mainly of the IgA class but the total immunoglobulin concentration was 20 times less than in the blood. Paired samples of blood serum and bile were collected from rats at various times after antigens had been injected into the Peyer’s patches, the spleen, or the subcuticulum. Between 5 and 10 days after killed bacteria had been injected into the Peyer’s patches, specific agglutinins appeared in the bile in titres that often were as high as those in the blood, and much higher than those in the bile of rats that had been immunized by other routes. By using specifically purified, radiolabelled antiglobulin reagents it was shown that the antibodies in the bile were mainly of the IgA class, whilst those in the blood were of the IgG and IgM classes. A similar distribution of antibody isotypes was found after allogeneic white cells had been injected. Substantial amounts of alloantibodies of the IgA class were found in the bile but not in the blood; in addition, the bile contained significant amounts of antibody associated with IgM. Thus, by injecting antigens into Peyer’s patches and collecting the bile it is easy to obtain specific, secretory antibodies in the amounts needed for the investigation of their functions in vitro and in vivo.