146 IMMUNOLOGY 



substance (body protector), immune body (Pfeiffer), sensitizer 

 (Bordet), and amboceptor (Elirlich). Bordet showed that if he 

 vaccinated guinea pigs with a killed vaccine, the protective sub- 

 stance or sensitizer appeared in their blood after the lapse of 

 several days and that it was the same as the sensitizer found in 

 the blood of animals recovering from infection. 



It is now possible to develop these simple definitions: 



1. Bacterial Amboceptor, Immune Body or Sensitizer. — This is 

 a thermostable substance found frequently in small amouiits in the 

 blood of normal animals but more frequently and in much greater 

 concentration in the blood of vaccinated animals or animals which 

 liave recovered from an infection. It has a specific affinity for the 

 bacteria used in the vaccine or Avliich caused the infection and Ity 

 combining with them renders them susceptible to union with a nor- 

 mal enzjnne-like substance called complement which kills and in the 

 case of cholera vibrios dissolves the bacteria. 



2. Sensitized Cells. — When bacteria or any cellular antigen is 

 united to its antibody or sensitizer it is then a sensitized cell. 



3. Complement. — This is a thermolabilc enzyme-like substance 

 found in the blood of all Avarm-blooded and some cold-])looded 

 animals. It will combine with seiLsitized cells and bring about their 

 death or lysis. 



Further Studies on Normal Bacteriolytic Substances. — In addi- 

 tion to tiie alpha hjsins whicli require thermolabile complement for 

 their activity other lytic agents such as p hjsins, leukins and 

 lysozyme have been described. Eacli of tliese would seem to merit 

 a brief discussion. 



Alpha Lysixs. — The question arose quite early as to whether the 

 lytic mechanism described by Bordet for immune lysins would 

 apply to normal lytic agents. i\Iuir and Browning (1908) working 

 with guinea pig serum, concluded that the mechanism of normal 

 bactericidal action was similar to the bactericidal action of immune 

 serum. They further concluded that bactericidal complement 

 (termed by them "bacteriophilic" complement) and hemolytic 

 complement are separated varieties. Other research such as that of 

 Irwin, Beach and Bell (1936), or Shrigley and Irwin (1937), and 

 of Dingle, Fothergill and Chandler (1938) tends to substantiate 

 this conclusion. Mackie and Finkelstein (1931, 1932) carried out 



