These specific memory responses are generally divided into humoral and cell-mediated immunity. Humoral immunity refers to the immunity conferred by the B-lymphocyte cells produced by the lymph system. These lymphocytes, also called the B-cells , produce antibodies. Antibodies are small proteins that can deactivate antigens by a variety of mechanisms, usually by binding with them. These lymphocytes, also called T cells , directly or indirectly destroy viruses, malignant cells, cells infected with intracellular organisms, and cells of grafted organs.
Macrophages are white blood cells with a number of important functions.
Without this macrophage processing, the T and B cells could not respond to some types of antigens. NK cells are cytotoxic to tumor cells and virus-infected cells. Many cells in the immune system produce chemicals that aid in regulating the immune response. These substances are referred to as mediators and broadly referred to as cytokines . Many cytokines are under study, to determine their effect on the immune system.