How does the immune system work? What are the molecular and cellular components and pathways that protect an organism from infectious agents or cancer? This comprehensive course answers these questions as it explores the cells and molecules of the immune system. The topics discussed during the first half of the course cover the structure, function, and genetics of the molecules of the immune system, including antibodies, B- and T-cell receptors, major histocompatibility complex (MHC) proteins and cytokines; and processes of lymphocyte development and antigen presentation. During the second half of the course the lectures focus on how the individual components of the immune system work together to fight bacterial, fungal, or viral infections. In addition, basic concepts of tumor immunity, immune system deficiencies, AIDS, and autoimmunity are examined. The course emphasizes the research and development opportunities for therapeutic intervention arising from recent advances in immunology (for example, the application of therapeutic antibodies and recombinant molecules as potential drug treatments). Upon completion of the course students have a sound understanding of the essential elements of the immune system, preparing them to engage further in this rapidly evolving field.