102 lABORATORY COURSE IN SERUM STUDY 



will fix complement so that the subsequently added red cells 

 sensitized by their appropriate hsemolytic immune-body will fail 

 to be laked, because no free complement is available. Neither the 

 antigen alone nor the antibody alone will fix complement in this 

 manner. 



Unfortunately bacterial cell bodies (like many other sub- 

 stances) if in sufficiently large amounts will of their own accord, 

 probably for purely physical reasons, absorb complement, in a 

 non-specific way, i.e., without the presence of a specific antibody. 



For this reason before doing a Bordet-Gengou reaction (and, 

 as will be seen later, in all complement fixation work) it is neces- 

 sary to determine the degree to which such non-specific comple- 

 ment fixation will take place with the given antigen and to use 

 in the actual test an amount too small to give such a false reaction. 



Experiment 1 



PRELIMINARY DETERMINATION OF NON-SPECIFIC COMPLEMENT BIND- 

 ING POWER OF BACTERIA 



Emulsify a 24 hour agar slant of typhoid bacilli in 10 c.c. of salt 

 solution. Heat at 60 C. for 30 minutes. 



Bring the volumes all to 1 c.c. with salt solution. Incubate 1 hour at 

 37 C. Add to each tube 0.5 c.c. of 5 per cent sheep cells sensitized 

 with 2 units of amboceptor (as determined in Lesson IV). Incubate 

 1 hour at 37 C. 



Experiment 2 



BORDET-GENGOU PHENOMENON 



Dilute some of serum of the typhoid immune rabbit (whose prepara- 

 tion was begun in Lesson I) 1 to 10 with saline. If 0.2 c.c. of bacterial 

 emulsion was found in the preliminary test not to interfere at all with the 



