Immunology, historical notes. The immune system: general features. Innate Immunity vs Adaptive Immunity. Innate immunity. Blood and tissue defense cells: leukocytes, dendritic cells, macrophages, mast cells. The complement, classic activation, alternative and way of the lectins. Anatomical barriers to infections, mechanical removal of microorganisms, and 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. T4 lymphocytes and T8 lymphocytes. B lymphocytes. Overview of the steps involved in activating the adaptive responses. Humoral immunity. The 5 antibody classes. Origin of antibody variability. Clonal selection and clonal expansion. Mechanisms of action of antibodies. Cell-Mediated immunity. Activation of cytotoxic T cells and macrophages. Immune memory. Hypersensitivity. Passive, active, natural and artificial immunity. Vaccines and vaccination.