Immunoregulation is one of the areas which has witnessed the most explosive advances of immunology during the past decade. It is in this area that the current view of the immune system has arisen and developed. There is indeed little doubt that immune reactions are primarily determined by messages which are genera ted within the immune system and passed among different types of immunologie cells. This cell communication not only determines the type, intensity and duration of the response after perturbation of the immune system by exogenous antigens, but it is also essential for preventing...