This work presents the evidence for the belief that psoriasis is a disease of abnormal keratinocyte proliferation induced by T cells. The latest approaches to investigating the immunopathogenesis of this disease, and a review of previous findings, are presented to give an overall picture of the current knowledge in this field. Each topic is discussed in detail, clearly illustrated and well referenced. The book should be useful to clinical dermatologists and researchers in the fields of immunology and dermatology who have an interest in skin diseases.