To establish the specificity of cytotoxic responses by T cells in the presence of HER2-BsAb, HER2(−) breast carcinoma HTB-132 cells and HER2(+) MCF-7 cells were tested in a cytotoxicity assays using ATCs (E:T ratio of 10:1) and HER2-BsAb at decreasing concentrations (Fig. 1D). The gene discussed is ERBB2; the disease is breast carcinoma.