Utilizing our novel ELISA, we detected tumor-specific antibodies at concentrations as low 10 ng/mL (Figure 1 , C), demonstrating comparable sensitivity to flow cytometric or immunocytochemical methods. Additionally, we validated our ability to identify tumor-reactive antibodies from our patient cultures, compared to equal amounts of non-specific IgG and culture media (Figure 1 , D). We also examined the potential applicability of this method to identify tumor-specific antibodies in other cancers using the mammary carcinoma cell line SK-BR-3, which highly expresses the cell surface tumor-associated antigen HER2/ neu [37] . Trastuzumab (Herceptin TM ), a humanized antibody specific for HER2/neu, was specifically detected compared to an equal amount of a control IgG employing our method (Figure 1 , D). Thus, we demonstrate that we can detect antibodies against tumor cell antigens in a sensitive, specific and reproducible manner.