Book Description: This purpose of this text is twofold: to illustrate in a clinical context essential points about the mechanisms of immunity; and to describe and explain some of the immunological problems most commonly seen in a clinical environment. Each case is genuine, drawn mainly from records of two major US hospitals: The Boston Children's Hospital and the Brigham and Women's Hospital. The presentation format for each case is the same; case history proceeds basic scientific facts that are required to understand the case, followed by a brief summary of the disease under study. Each case ends with the questions and discussion points highlighting the lessons learnt from the case.