Pxeumococcus Antigen 



379 



Three doses were given, the total corresponding to 50 to 75 

 billion of killed pneumococci. Practically no local, and absolutely 

 no general reaction was observed after any of the injections. 

 Following the injection of antigen protective substances against 

 the three fixed types of pneumococcus could be demonstrated in 

 the serum of the volunteers. 



The pneumococcus antigen is not adsorbed by Lloyd's reagent, 

 and does not diffuse through a collodion membrane. 



Saline suspensions of pneumococcus Type I which had been 

 stored in the refrigerator for several months were shown to con- 

 tain a large amount of the antigen in the supernatant fluid. 

 Mice were injected subcutaneously with two or three doses of 

 the supernatant fluid which protected them against a hundred 

 thousand lethal doses of a broth culture of pneumococcus Type I, 

 injected intraperitoneal^. Some of the immunizing antigen is 

 retained by the killed pneumococci. 



A chemical analysis of the supernatant fluid from old pneumo- 

 coccus vaccine gave the following result: Total nitrogen, 13 

 mg. per 100 c.c, non-protein nitrogen, 12.9 mg. per 100 c.c, 

 of which 8 mg. were in the form of amino acid nitrogen. Phos- 

 phate present. Reaction P H 7.8. Biuret, Millon, Xanthoproteic 

 and Hopkins-Cole reaction were all negative. Precipitation tests 

 with heat and acid, sulphosalicylic acid, potassium ferrocyanide 

 and acetic acid were all negative. A slight turbidity is produced 

 by 9 volumes of 95 per cent, alcohol, trichloracetic acid, cone, 

 hydrochloric and nitric acid. The precipitate produced by 9 

 volumes of alcohol was found to be chiefly phosphates. 



The filtrate from old pneumococcus vaccine gives clear cut 

 precipitin reaction with homologous antiserum in antigen dilu- 

 tions up to 1 :120. 



The immunizing antigen of the pneumococcus and the precipi- 

 tinogen appear to be two distinct entities, as we have encoun- 

 tered some pneumococcus antigen solutions which fail to give 

 precipitin reaction with homologous antiserum, but produce im- 

 munity in mice when injected subcutaneously. 



