Immunology focuses on the study of immunology. The first half of this book provides a treatise of basic immunology, while the rest is more clinically orientated and illustrates the importance of immune mechanisms for health and disease. This text emphasizes the three good reasons why immunology should be studied. First is that man cannot survive without immunological defense against foreign material. Second is that these same immunological defense mechanisms can cause various forms of tissue damage that result in different diseases. Finally, some immunological reactions can be used as sensitive and highly specific methods for analytical and diagnostically useful determinations of low molecular substances. This publication is primarily intended for students of medicine and natural sciences, as well as clinicians concerned with the field of immunology.