HOST RESPONSE TO ANTIGENIC ACTION 437 



phagocytosis of twenty-four-hour cultures by normal blood, the 

 anticarbohydrate antibody tends to predominate as the pneumo- 

 cocci approach the state in which they exist in the animal body. 

 Enders and Wu 362 later reported (1934) that the opsonic titer of 

 normal human serum could be practically eliminated by the addi- 

 tion of the A carbohydrate, that is, the acetylated capsular poly- 

 saccharide of Pneumococcus. 



Naturally Induced Immunity 



SPECIFIC ANTIBODIES IN THE BLOOD DURING PNEUMONIA 



Pneumococcus, upon entering the animal body and inciting mor- 

 bid processes in the organs and tissues, by virtue of its several 

 components arouses or stimulates physiological functions latent 

 or active leading to immunity, and the products of the freshly ac- 

 tivated functions may be detected and measured by the various 

 serological reactions. The first intimation that immune substances 

 arise in man as a result of pneumococcal infection came from the 

 work of the Klemperers, 725 who discovered that serum taken from 

 pneumonia patients after crisis displayed curative properties for 

 experimentally infected rabbits. Similar protective antibodies were 

 observed in the serum of pneumonia patients by Romer, 1155 in some 

 cases several days after the onset of the disease. Then Neufeld and 

 Haendel 990 succeeded repeatedly in demonstrating not only that 

 there was a decided increase in protective substances for the mouse 

 in the serum of pneumonia convalescents soon after crisis, but that 

 the action was specific for heterologous as well as for homologous 

 strains of pneumococci. The authors, therefore, were convinced 

 that the crisis in lobar pneumonia depended upon the formation 

 and specific action of antibodies. Seligman (1911 ), 1253 on the con- 

 trary, found no difference in the degree of protective action of se- 

 rum taken before or after the critical period. Strouse (1911), 1346 

 using the Neufeld technique, was unable to detect opsonins in 

 heated post-critical serum. However, after sensitizing the pneumo- 



