Immunology, Background. General features of the immune systems: Innate vs adaptive immunity. Innate immunity. Defence Cells in blood and tissues: white blood cells, dendritic cells, macrophages, mast cells. The complement system: classical, alternative, and lectins activation. Anatomic barriers to infection, mechanical removal of microorganisms, bacterial antagonism. PAMPS, PRR, cytokines. Phagocytosis. Natural killer cells. Inflammation, fever, acute phase response. General information on the lymphatic system. Antigens, immunogens and lymphocyte receptors. Adaptive Immunity. The major histocompatibility complex. Antigen-presenting cells. Lymphocytes T4 and T8 lymphocytes. B lymphocytes. Overview on the steps involved in the activation of adaptive responses. Humoral immunity. Antibody classes. Origin of antibody variability. Clonal selection and clonal expansion. Mechanisms of action of antibodies. Cell mediated immunity. Activation of cytotoxic T lynfocytes and macrophages. Immune memory. Hypersensitivity. Passive, active, natural and artificial Immunities. Vaccines and vaccination.