Immunology has been written primarily for undergraduate students of biotechnology and biochemistry as also medicine. The book provides an in-depth coverage of the fundamental concepts of immunology, suitably aided with numerous illustrations and exhibits. The initial chapters of the book provide a broad overview of the immune system and its functioning. The subsequent chapters discuss antibodies, the major histocompatibility complex (MHC), antigen receptors, cytokines, lymphocyte activation, immune responses against pathogens, and the manipulation of the immune system by various vaccine strategies. The book also delves into hypersensitivity states, immunodeficiency disorders with special emphasis on the HIV-AIDS pandemic, transplantation, and tumour immunology. Tolerance and autoimmunity have been linked for a better understanding of the mechanisms that lead to autoimmune diseases. Owing to its comprehensive coverage, this book would be useful to postgraduate students of biochemistry, biotechnology, and microbiology as also researchers.