HOST RESPONSE TO ANTIGENIC ACTION 441 



tient, the antibody might appear spontaneously in the blood serum 

 as early as the third or fourth day of the disease and crisis and 

 recovery might be delayed until the sixth to the tenth day. How- 

 ever, recovery might occur without demonstrable protective sub- 

 stance in the blood of patients whose serum later developed protec- 

 tive properties. According to Lord and Persons, the amount of 

 antibody appearing in the course of pneumococcal pneumonia was 

 small and it might be present in the blood concurrently with sep- 

 ticemia. The formation of protective substances by the patient 

 gave no assurance that the infection would not progress to a fatal 

 termination. 



In empyema fluids of pneumococcal origin, Floyd (1920) 456 

 demonstrated the presence of specific precipitin and of much 

 smaller amounts of agglutinin, and considered that their occur- 

 rence was generally a favorable prognostic sign. Later, Finland 441 

 reported (1932) that sterile pleuritic exudates from patients with 

 lobar pneumonia contained actively acquired antibodies similar to 

 those developing in the blood serum. 



A property of the serum of pneumonia patients which had es- 

 caped previous notice was the capacity to precipitate in high titer 

 the non-protein somatic substance — the C Fraction — derived from 

 pneumococci. Tillett and Francis (1930) 1409 tested serum obtained 

 from patients during illness and convalescence for antibodies spe- 

 cifically reactive with this chemically distinct carbohydrate of 

 Pneumococcus. The results, when correlated with the course of the 

 disease, demonstrated differences in the occurrence of each qualita- 

 tively distinct antibody. Strangely enough, the precipitating ac- 

 tion of the serum on the somatic carbohydrate developed in the 

 very early stages of the disease, only to disappear at the time of 

 crisis. Precipitation of Fraction C was not limited to the serum 

 of individuals ill with pneumococcal infection and, in the few cases 

 available for comparative tests, definite reactions were obtained 

 only in streptococcal and staphylococcal infections and in acute 

 rheumatic fever. 



