46 



III.— THE SIGNIFICANCE OF SEROLOGICAL DIFFER- 

 ENCES AMONGST PNEUMOCOCCI. 

 By Arthur Eastwood, M.D. 



PAGE 



Introduction ..--------46 



General Ideas about Antigens and Antibodies - - - -47 



Chemical Specificity -------- 48 



Chemical Instability -------- 50 



The " Mosaic Pattern " Theory 51 



A further Antigenic Requirement - - - - - 54 



Influence of Physical Conditions on Specificity - - - 55 



Possible Limitations of the Antigen-antibody Conception - 59 



Discussion of Pneumococcal Antigens and Antibodies - - - 63 



Antigenic Varieties or Variants - - - - - - 63 



Chemical and Colloidal Instability - - - - - 64 



Therapeutic Value of Pneumococcal Antibodies - - - 67 



Summary and Conclusions - - - - - - - 71 



Method 71 



General Principles 72 



Pneumococcal Antigens and Antibodies - - - - 74 



Introduction , 



Research on pneumococci is intimately concerned with a 

 serological complication which has arisen from the discovery of 

 antigenic differences amongst members of the species. By 

 selective tests, in which concordant results are obtained with 

 agglutination, precipitation, and protection for mice, a large 

 number of different " serological races " has been demonstrated; 

 in fact, the number of possible varieties appears to be so large 

 as to make an inclusive classification impossible. 



This is a matter of importance practically as well as theoretic- 

 ally, because it appears to involve difficulties in the preparation 

 of therapeutic sera. If the main factor in the production of a 

 useful serum were some specific substance common to all virulent 

 pneumococci, one would expect an antiserum prepared from 

 a single typical strain to be polyvalent in its protective and 

 therapeutic action; and then minor antigenic differences might 

 be disregarded. But this expectation has not been realised. 

 On the contrary, there is a large accumulation of laborator}' 

 evidence in support of Neufeld's original contention that an 

 immune serum is useful only against strains which are identical, 

 in every antigenic respect, with the strain used for immunisation. 



Hence one cannot dismiss this difficulty by merely offering 

 the suggestion, which has been made about the " serological 



