As a phylogenetically old system complement is now regarded as a part of innate immunity. But it is much more than that. It bridges innate and adapted immunity, participates not only in host defense but also in many essential physiological processes, old and new diseases and adverse conditions. Indeed, complement became a term that almost defies categorization. What was for a long time a subject for a limited number of specialists has now moved into the mainstream of experimental and clinical immunology. In 1973 I visited the Basel Institute of Immunology and met its director, the eminent...

As a phylogenetically old system complement is now regarded as a part of innate immunity. But it is much more than that. It bridges innate and adapted immunity, participates not only in host defense but also in many essential physiological processes, old and new diseases and adverse conditions. Indeed, complement became a term that almost defies categorization. What was for a long time a subject for a limited number of specialists has now moved into the mainstream of experimental and clinical immunology. In 1973 I visited the Basel Institute of Immunology and met its director, the eminent...