AMBOCEPTORS 325 



an immune serum and a fresh normal serum. This procedure presents 

 certain difficulties, and the subject is considered more fully in the chap- 

 ter on Passive Immunization. 



Anti-amboceptors. Just as anti-agglutinins and antiprecipitins 

 may be formed, so anti-amboceptors may be produced experimentally 

 by immunizing an animal with an amboceptor-laden serum. An anti- 

 amboceptor is specific for the amboceptor that caused its production, 

 and when these are mixed, the activity of the amboceptor is impeded by 

 the anti-amboceptor, which unites with its cytophilic group. It is 

 possible that old erythrocytes are destroyed by an autohemolysin present 

 in the blood-stream under normal conditions, and that a physiologic 

 equilibrium is maintained through the production of an anti-amboceptor. 



QUANTITATIVE ESTIMATION OF AMBOCEPTORS 



Titration of a Hemolytic Amboceptor. The quantity of amboceptor 

 in a given amount of serum may be determined by titration. If, for 

 instance, a rabbit is injected with sheep corpuscles, the amount of hemo- 

 lytic amboceptor for these cells in the rabbit serum may be determined 

 by the following method of titration: To a series of test-tubes increasing 

 amounts of the rabbit immune serum (heated to remove complement) 

 are added, with a constant dose of sheep-cells and a constant dose of 

 fresh guinea-pig serum to furnish complement. After a suitable period 

 of incubation the tube showing complete hemolysis would contain suf- 

 ficient hemolytic amboceptor, i. e., just one unit. The value of the 

 immune serum may then be expressed by stating that so much serum, 

 as, e. g., 0.001 c.c., contains one unit of amboceptor. Of course, if the 

 amounts of complement or corpuscles are varied the unit will likewise 

 vary. In order to establish or measure the content of hemolytic am- 

 boceptor a constant amount of corpuscles and complement must be 

 used. The details of this amboceptor titration are given in the chapter 

 on Hemolysins. 



Titration of a Bacteriolytic Amboceptor. A bacteriolytic amboceptor 

 may be measured in much the same manner as a hemolytic amboceptor, 

 although less accurately, because of technical difficulties. If a standard 

 and fixed dose of an emulsion of living bacteria and a fixed dose of com- 

 plement are mixed with varying amounts of inactivated immune serum 

 containing amboceptors for these bacteria, the amount of amboceptors 

 present may be determined by plating the mixture and estimating the 

 number of bacteria that have been killed. Or we may use fixed doses of 

 immune serum and complement with varying amounts of bacteria and 



