Immunology is the study of the immune system of higher organisms in relation to disease. Specifically, immunology can be defined as the branch of biology that is concerned with the structure and function of the immune system, the bodily distinction of self from non-self, and the use of antibody-based laboratory techniques or immunoassays. In general, the immune system of higher organisms can be broken down into two primary response systems that work together to create immunity. The two primary response systems are innate and adaptive immune responses, with the latter further divided into cell-mediated and antibody-mediated responses. The cell-mediated response is produced when a subset of sensitized white blood cells or lymphocytes directly attack material (e.g., usually a cell or a virus) that has been determined to be foreign to the body. The antibody-mediated response involves the transformation of a subset of lymphocytes into cells that produce and secrete specific antibodies against the foreign material. These two immune responses are triggered when foreign material is introduced into the host as depicted.