Book excerpt: Immunodermatology is a field covering the majority of skin diseases, including the most prevalent onesin the general population. The Second Edition of Skin Immune System (SIS) discusses immune-mediated skin diseases and disease groups in which the SIS plays a role. It covers major findings in immunophysiology and immunopathology that have occurred since the introduction of the First Edition in 1990. As the subtitle indicates, the Second Edition adds a new emphasis on cutaneous immunology, and also includes new information on immune-based therapeutic interventions and methods, such as phototherapy and the immunological therapy of skin cancer. The book contains Part I, with introductory chapters; Part II, with descriptions of the cellular elements; and Part III, which describes the humoral and molecular components of SIS. Part IV follows to integrate the facts described in Parts II and III into concepts of pathophysiology. It contains a number of concepts entitled "response patterns" that describe how the constitutional elements of SIS work together. New in this edition are the descriptions of immunodermatological diseases individually described in Part V. Part VI is also all new and summarizes principles of immunotherapy.