Immunology is a nodal subject that links many areas of biology. It permeates the biosciences, and also plays crucial roles in diagnosis and therapy in areas of clinical medicine ranging from the control of infectious and autoimmune diseases to tumour therapy. Monoclonal antibodies and small molecule modulators of immunity are major factors in the pharmaceutical industry and now constitute a multi billion dollar business. Students in these diverse areas are frequently daunted by the complexity of immunology and the astonishing array of unusual mechanisms that go to make it up.