An overview -- The innate immune system -- The innate immune system -- B cells and antibodies the magic of antigen presentation -- Magic of antigen presentation -- Activating t cells -- T cells at work -- Secondary lymphoid organs and lymphocyte trafficking -- Restraining the immune system -- Tolerance induction and MHC restriction -- Immunological memory -- The intestinal immune system -- Vaccines -- The immune system gone wrong -- Immunodeficiency -- Cancer and the immune system.