Immunology is a branch of biology, which is concerned with the study of the immune system. The malfunctions of the immune system cause immunological disorders such as immune deficiency syndromes, hypersensitivities and transplant rejection. Immunological disorders fall into the broad categories of immunodeficiency and autoimmunity. In an immunodeficiency disease, the immune system fails to provide an adequate response. Some examples of immunodeficiency diseases are primary immune disease and chronic granulomatous disease. In autoimmune diseases, the immune system attacks its host’s body such as in Hashimoto's disease, systemic lupus erythematosus, myasthenia gravis and rheumatoid arthritis. Different approaches, evaluations, methodologies and advanced studies on immunology have been included in this book. There has been rapid progress in the understanding of immunological disorders, their diagnoses and treatments, which have been included in this extensive book. It is an essential guide for both academicians and those who wish to pursue this discipline further.