The book is written in a very simple and lucid manner so that everybody can read and understand the Immunology subject very easily. The book is useful for scientist, teachers, students, officers, diagnosticians and researchers as Immunology has become an essential and indispensable subject now a days not only to understand the different arms of the immune system playing a role in the pathogenesis of the diseases but also to diagnose and treat the diseases in a efficient and effective manner.This book will provide information on all the aspects of the Immunology such as Elements of innate and acquired immunity, Antigens and antigenicity, Antibody structure and functions, Complement, Serological tests, origin, morphology and functions of T and B lymphocytes, Cytokines, Defects in immune system, AIDS, Autoimmunity and tolerance, Tumour immunology, Vaccines and vaccinations besides a large number of questions of miscellaneous nature.A list of tests recommended for infectious diseases in international trade has also been included for ready reference of researchers, teachers and students as well. Lastly it will be helpful for all to understand the Immunology subject easily and to face various competitive examinations with a greater degree of confidence.