82 IMMUNE SERA 



plement necessary. We may say say, therefore, 

 that that group of the amboceptor which combines 

 with the red cell has a stronger affinity than that 

 which combines with the complement. 



Role of the Amboceptor. According to Ehrlich, 

 then, the r61e of the amboceptor consists in this, 

 that it attaches itself to the red cell on the one hand 

 and to the complement on the other, and in this way 

 brings the digestive powers of the latter to bear 

 upon the cell, the complement possessing no affinity 

 for the red cell. Amboceptor and complement 

 have no great affinity for each other. At o C. they 

 may exist side by side, cell-amboceptor-complement 

 combining only at higher temperatures. 



The amount of amboceptor which combines 

 with the red cells may vary greatly, as the experi- 

 ments of Bordet and of Ehrlich clearly show. Some 

 red cells combine with only just enough amboceptor 

 to effect their solution. Others are able to so sat- 

 urate themselves with amboceptor that they may 

 have a hundred times the amount necessary for 

 their solution. 



On what the Specificity Depends. From the pre- 

 ceding it follows that the specific action of the 

 haemolytic sera, and of the bactericidal sera also, is 

 due exclusively to the immune body. This pos- 

 sesses a combining group which is specific for the 

 cells with which the animal was treated; e.g., 

 the combining group of an amboceptor produced 



