290 STREPTOCOCCUS-PNEUMOCOCCUS GROUP 



Immunity and Immunization. Relatively little is known of the 

 nature and extent of immunity following recovery from an attack 

 of pneumonia. One attack appears to predispose somewhat to a sub- 

 sequent attack, which was explained formerly on the basis that little 

 or no immunity was conferred on the patient. The extensive work 

 of Cole and his associates suggests that a second attack of the disease 

 may be caused by a different type of pneumococcus; their experiments 

 indicate that antibodies specific for one type are not protective against 

 infection with the other types. 



The serum of convalescent pneumonia patients exhibits relatively 

 feeble bactericidal activity, even upon the homologous strain of the 

 pneumococcus, and the mechanism which leads to recovery is not 

 definitely known. Neufeld 1 and others have advanced the hypothesis, 

 based upon careful observation, that the crisis in pneumonia, which 

 usually marks the end of the prominent clinical symptoms, is asso- 

 ciated with a somewhat abrupt increase in the amount of specific 

 opsonin of the blood an increase in bacteriotropins in Neufeld's 

 terminology. This theory assumes that leukocytes play a prominent 

 part in the healing process, and that phagocytic activity becomes 

 efficient at or about the time of the crisis. 



Neufeld and Handel, 2 and Cole and his associates 3 have produced a 

 serum which protects susceptible animals, as mice, against many 

 times the fatal dose of the homologous strain of organism by injecting 

 gradually increasing doses of very virulent pneumococci into horses. 

 Cole has used these sera clinically in the treatment of pneumonia 

 with promising results in infections caused by Types I and II of the 

 pneumococcus. The serum appears to destroy or greatly reduce the 

 number of pneumococci in the blood, and to be of material benefit in 

 reducing the severity of the infection. At present a satisfactory 

 serum for infection with Type III, Pneumococcus mucosus, has not 

 been prepared. Cole specifically directs attention to the necessity 

 of identifying the type of infecting organism (by agglutination reac- 

 tions) before administering the serum. It is imperative that the 

 homologous serum be used. 



Bacteriological Diagnosis. Pneumococci are found in* the healthy 

 throats of a very considerable percentage of adults, consequently the 

 identification of pneumococci in the sputum is of little clinical signifi- 



1 Zeit. f. Immunitatsforsch., 1909, iii, 159. 



2 Arb. a. d. kais. Gesamte, 1910, xxxiv, 169. 



3 Jour. Am. Med. Assn., 1913, Ixi, 663; New York Med. Jour., January 2 and 9, 

 1915. 



