Human monoclonal antibodies derived from pleural effusion lymphocytes of a patient with breast carcinoma react with human breast cancer-associated antigens and mouse mammary tumor virus polypeptides

Four human hybridoma cell lines (PEB_1-4) were established from a fusion of pleural effusion lymphocytes isolated from a breast cancer patient with metastatic disease, 6 years postmastectomy. The hybridomas secreted IgG-k (3 μg/ml/10⁶ cells). These monoclonal antibodies (PEB_1-4) reacted to different degrees with mouse mammary tumor virus (MMTV) and T47D particles (HuMTV). Immunological cross-reaction was also detected with antigens isolated from body fluids of breast cancer patients (BF-Ag). The binding capacity of the monoclonal antibodies (MAbs) PEBj_4 to the above-mentioned antigens was measured by RIA. The specificity of these antibodies was further demonstrated by radioim-munoprecipitation of MMTV, T47D (HuMTV) and BF-Ag. The binding of PEB_1-4to surface antigens of intact cells grown in culture was measured by RIA. Some of the MAbs were shown to bind more avidly to breast cancer cells than to nonbreast cancer cells or nonmal-ignant cells. The PEB_1-4human monoclonal antibodies may be found useful in analyzing the virus-breast cancer relationship.