398 BIOLOGY OF PNEUMOCOCCUS 



ANTIOPSONINS 



The existence of substances in Pneumococcus inimical to leuco- 

 cytic ingestion became apparent to Rosenow (1907) 1161 who, by 

 saline extraction or by autolysis of the cocci, obtained a substance 

 or substances that inhibited opsonic action. It was found further 

 that avirulent strains could absorb the inhibiting substance and 

 then become resistant to phagocytosis, while after similar extrac- 

 tion virulent organisms acquired the capacity to absorb opsonin 

 and became vulnerable to the destructive action of the white blood 

 cells. The presence of substances in pneumococci capable of inhib- 

 iting phagocytosis was demonstrated by Tchistovitch and Youre- 

 vitch 1383 in 1908. When saline suspensions of washed, virulent 

 pneumococci were added to serum-leucocyte mixtures, marked 

 phagocytosis resulted, but when a small amount of the washings 

 from the original culture was added to the combination the cocci 

 were no longer ingested by the leucocytes. The inhibiting sub- 

 stances were found only in cultures of virulent strains, they were 

 specific for the bacterial species and were thermostable. For such 

 substances Tchistovitch proposed the name "Antiphagins." 



Pritchett 1110 endeavored to develop antiopsonins in rabbits by 

 injecting them with antipneumococcic horse serum, but could ob- 

 tain no evidence of the formation of substances antagonistic to the 

 action of immune serum. On the contrary, the serum of rabbits in- 

 jected with antipneumococcic horse serum for Type I, II, or III 

 pneumococci, when combined with antipneumococcic serum for 

 Types I and II, increased opsonization of organisms of Types I 

 and II but in this respect never affected strains of Type III. 



Confirmation of the existence of antiopsonic principles in viru- 

 lent pneumococci is to be found in the experiments of Wadsworth 

 and Sickles, 1475 and of Sickles (1927). 1277 Intracellular substances 

 released by sodium oleate solution of the organisms, or present in 

 the sterile filtrates of broth cultures, prevented phagocytosis of 

 pneumococci in immune-serum and leucocyte mixtures. There was 

 some evidence of type-specificity in the action of the pneumococcal 



