Blood obtained from volunteers will be used as a source of neutrophils and natural killer (NK) cells necessary for an ADCC assay. Cytotox-96 kit from Promega Corporation (Madison, WI) will be used for this assay. This assay involves target cells (e.g cells from the breast cancer cell line SKBR-3), IgG antibodies directed against antigens on the cells, and effector cells (NK cells or neutrophils) from blood donors.