282 INFECTION AND IMMUNITY 



Because of their action in preparing the bacteria for ingestion by the 

 leucocytes, he named these bodies " opsonins " {Sipwvitu^ to prepare food). 



Neufeld and Rimpau^ soon after, and independently of Wright, 

 described similar substances in the blood serum of streptococcus and 

 pneumococcus immune animals, which they called bacteriotropins. 

 Because of their greater thermostabihty it is not yet possible to identify 

 these bacteriotropins absolutely with the opsonins. 



The importance of these opsonic substances in immunity was shown 

 by Wright ^ in a series of experiments in which he determined that in 

 persons iU with staphylococcus or tubercle-bacillus infections, the phago- 

 cytic powers were relatively diminished toward these microorganisms, 

 but could be specifically increased upon active immunization with dead 

 bacteria or bacterial products. 



The results of Wright have been confirmed and elaborated by nu- 

 merous workers. 



The diminished power of leucocytes to take up bacteria without the 

 co-operation of serum was demonstrated, after Wright, by Hektoen and 

 Ruediger,^ who worked with gradually increasing dilutions of serum. 

 The contention of the Wright school, however, that leucocytes are en- 

 tirely impotent for phagocytosis without the aid of serum, can not be 

 regarded as proven, in face of the work of Lohlein ^ and others who 

 have observed phagocytosis on the part of washed leucocytes. 



The specificity of opsonins and their multiplicity in a given serum 

 were shown mainly by the work of BuUock and Atkin,^ Hektoen and 

 Ruediger," and Bullock and Western.' These authors showed that the 

 opsonic substances in sera could be absorbed out of the sera, one by one, 

 by treatment with various species of bacteria, a procedure analogous to 

 the method of absorption used in the study of agglutinins. 



The increase of phagocytic power demonstrated by Wright in immune 

 sera naturally led to the question whether this depended merely upon 

 an increase of the normal opsonins or whether the newly formed immune 

 opsonins were entirely different substances. The greater thermosta- 

 bility of the opsonins in immune sera seemed, at first, to support the 



> Neufeld und Rimpau, Deut. med. Woch.., xl, 1904. 



2 Wright and Douglas, Proc. Roy. Soc, London, Ixxiv, 1905 



3 Hektoen and Ruediger, Jour. Inf. Dis., ii, 1905. 



» Lohlein, Ann. de rinst. Pasteur, 1905 and 1906. 



' BuUock and Atkin, Proc. Roy. Soc, London, Ixxiv, 1905. 



« Hektoen and Ruediger, loc. cit. 



» Bullock and Western. Proc. Roy. Soc, loc. cit. 



