The mainstream view of the immune system is concerned with molecular and cellular details resulting in a picture of immense complexity. Many immunologists live with this complexity, hoping that a series of breakthroughs will eventually add up to a greater insight. However, the forest is ignored for the trees and a 'Systems Approach' is vital for a better understanding. Peter Bretscher develops here a unique perspective on how the immune system functions as an integrated organ, by taking account of observations and concepts at the 'level of system' that are often half forgotten or ignored. A colleague, on reading this book, wrote: "Those who have followed Peter's work these past 50 years will recognize this book for what it really is - a rare achievement, a scientific masterpiece. It is a must read for all those Immunologists and Clinicians who want to find effective immunological cures for the many debilitating health issues that confront us. Peter Bretscher has produced a lucid and logical exposition of the rules governing how the adaptive immune system responds to all foreign antigens whether bacterial, viral or modifications of the self, which emerge in cancer or autoimmune conditions. This book is a testament to Louis Pasteur's dictum that there is no applied science, just the application of basic science." Rediscovering the Immune System is written in a jargon-free and accessible style. This personal perspective is an ideal guide to the immune system for students, researchers and the engaged, general reader alike.