ABSTRACT
The diversity of the repertoire of the immune system is immense. There are very few classes of molecules, natural or synthetic, which fail to elicit an immune response in mammals. This chapter presents a model of the immune system that emphasizes autoimmunity as normal process. It argues that stresses the symmetry of the immune system: self-antigens determine the immune repertoire of both T- and B-cells. The Major Histocompatibility Complex is an assembly of structurally different membrane antigens which allow recognition of cell-bound antigen by T-lymphocytes. Autoimmunity has been an important topic since 1900 when, for the first time, its immunological significance was recognized by Ehrlich and Morgenroth. Rapid advances have been made in elucidating the structure of the T-cell receptor as well as the mechanism that generates its clonally distributed diversity.
