Human monoclonal antibody JDB 1 reacts with cytoplasmic and membrane bound antigens present on a variety of human breast tumor cell lines

The human monoclonal antibody JDB₁ was examined for reactivity to five breast cancer cell lines as well as normal fibroblasts. The JDB₁ clone secretes both IgG₃ and IgM antibody. In these studies both the total antibody (containing IgG₃ and IgM) as well as the purified IgG₃ and IgM fractions were examined for tumor cell binding reactivity. Peroxidase staining was observed in the breast cancer lines SW527, MCF-7, T47D, SKBR3, and MDAMB231, while GM179 and GM5758 fibroblast lines were negative for antibody binding. Tumor cells were examined using two techniques: a drop cell technique in which cells were fixed onto slides and also a cover slip assay in which cells were grown onto sterile cover slips and subsequently stained with the human monoclonal antibody using a peroxidase technique. Both cytoplasmic and membrane staining were observed for all of the breast tumor cells tested using both assays. In addition, a cellular ELISA was developed and used to quantitate the binding of these antibodies to tumor cells.