Immunology is the study of the bodys protection from foreign macromolecules or invading organisms and the responses to them. These invaders include viruses, bacteria, protozoa or even larger parasites. In addition, immune responses are developed against our own proteins (and other molecules) in auto-immunity and against our own aberrant cells in tumour immunity. The first line of defence against foreign organisms are barrier tissues such as the skin that stop the entry of organism into our bodies. A second line of defence is the specific or adaptive immune system which may take days to respond to a primary invasion (that is infection by an organism that has not hitherto been seen). This book brings together new research from around the globe dealing with this extremely important subject.