PRODUCTION OF ANTIPNEUMOCOCCIC SERUM 569 



In 1921, at the International Conference on the Standardiza- 

 tion of Sera and Serological Tests in London, a committee of the 

 Health Organization of the League of Nations 506 drew up a plan 

 for the technique to be practiced in the assay of antipneumococcic 

 serum. At the Second International Serological Conference, 696 held 

 in Paris in 1922, it was believed that the titration test in mice, 

 when controlled by a standard serum, would provide a method for 

 standardization. Emphasis was placed upon the necessity of in- 

 cluding a control serum in every test. In 1923, a subcommittee of 

 the Health Organization of the League of Nations 597 proposed, as 

 a basis for international investigation, that, in performing the 

 mouse protection test, constant volumes of culture should be mixed 

 for five minutes with decreasing volumes of serum and the mix- 

 tures injected intraperitoneally into mice. The method* was found 

 in some instances to be satisfactory by Christensen, 847 but it failed 

 to receive universal recognition. 



In two articles dealing with the protective action of Type I anti- 

 pneumococcic serum in mice, Sickles (1927) 1276 " 7 stated that if 

 broth cultures, freed from organisms, were added to dilutions of 

 serum and the precipitate removed prior to use in the test, the pro- 

 tective action of the serum was diminished or neutralized. It is 

 probable that most, if not all, of this loss of activity was due to 

 absorption of antibody by the soluble type-specific and species- 

 specific substances although these were not emphasized as the fac- 

 tors responsible for the removal of protective antibody. It was 

 stated, however, that the reaction appeared to be associated with 

 that by which the precipitative elements of serum are absorbed 

 when treated with the homologous culture broth. 



Felton 406 utilized the principle in developing the technical details 

 of the neutralization method for assaying the antibody content 

 of antipneumococcic serum and concentrates. In the test, equal 

 amounts of a diluted, neutralizing culture and varying serum dilu- 

 tions are mixed and incubated at 37.5° for one to two hours. The 



* See Appendix. 



