Schematic representation of different types of cytotoxicity assays employed in this study. (A) Shows conventional ADCC against haptenized SK-BR–3 breast cancer cells via NIP-directed antibodies. FcR blocking antibodies served to identify trigger molecules involved in IgA-mediated ADCC. In (B), a novel reverse ADCC assay is shown using hybridoma target cells, which were selected for high membrane expression of their surface Ig directed to mouse κ light chains. In the presence of Fc receptor antibodies, these hybridoma cells are sensitized for reverse ADCC. (C) Shows recruitment of Fc receptor positive effector cells via BsAbs.