This book is a translation of the sixth edition of the textbook prepared by widely known scientists and teachers. It clearly outlines the basics of the functioning of the immune system in normal conditions and in pathology. The development of immunopathological processes is explained in detail: inflammation, autoimmunization, congenital and acquired immune disorders, infections, malignant neoplasms. New methods of targeted diagnostic and therapeutic interventions, developed and introduced into practice thanks to the latest molecular genetic achievements, are reflected. The textbook is illustrated with visual drawings and photographs presented in the form of original images of cells and molecules of the immune system.