Opsonins

Abstract

As you will all know there was a great divergence of opinions at the beginning of this century about the mechanism of antibacterial immunity. Metchnikoff has described the phenomenon of phagocytosis by the wandering cells, which seemed to occur in all multicellular organisms, and he beheved quite passionately that these scavenging cells were of predominant importance in defense against bacteria. Opposing views were held by Nuttal, Bürdet and others who were impressed by the fact that fresh serum from most mammals was rapidly bactericidal for many gram negative bacteria and that this effect was due to antibody and complement. Even when direct antibacterial effects could not be demonstrated in vitro they believed that antibody and humoral factors were the only determinants of bacterial elimination. In this they were no doubt influenced by the powerful and striking experiments of von Behring and Kitasato and the protection which diphtheria-antitoxin provided against the disease — simulating effect of the toxin. It remained for Almroth Wright to clarify the picture. By studying thein vitro interactions of bacteria and leucocytes he showed that for efficient and rapid phagocytosis to occur, serum was necessary in the system.