The book is a collection of up-to-date reviews by major researchers in the field of the fast-moving area of modern immunology. Its wide scope, depth of coverage, well-illustrated text, and the eminence of the authorship make it unique in its field. Over 1900 literature reference are cited. So much has happened in immunology since publication of the first edition of this popular book seven years ago that the second edition is a major new work. The chapters on mechanism and control of immunoglobulin genes by Fred Alt and his colleagues, T-cell antigen receptor genes by Mark Davis and Yeuh-hsui Chien, T lymphocyte signal transduction by Cox Terhorst et al, and the complement system by Ken Reid are all major updates and extensions of their first edition contributions. In addition, the second edition contains new chapters by David Jewell and Ian Wilson on the structure and function on MHC class I and class II antigens, by John Monaco on molecular mechanisms of antigen\nprocessing. By Gerry Klaus on B cell activation, and by Martine Verhoeyen and John Windust in recent advances by antibody engineering.