The Immune System, 3rd Edition is designed for use in immunology courses for undergraduate, medical, dental, and pharmacy students. This class-tested and proven textbook synthesizes the established facts of immunology into a comprehensible, coherent, and up-to-date account of how the human immune system works and the effects it has on the health and survival of individuals and populations, making generous use of medical examples to illustrate points. The reader-friendly text, full-color illustrations, and section and chapter summaries make the book accessible and easily understandable to students. The Third Edition is a major revision and includes two new chapters: Innate Immunity (Chapter 2) and Principles of Adaptive Immunity (Chapter 3). Former Chapter 12 has been divided into three chapters: vaccination (Chapter 14), transplantation (Chapter 15), and cancer (Chapter 16). The number of end-of-chapter questions has been expanded and now include essay, multiple choice, and case study (USMLE-format) questions with answers provided at the end of the book. "The Immune System" is adapted from "Immunobiology" by Janeway, Travers, and Walport.