258 COLLECTED STUDIES IN IMMUNITY. 



II. Amount of Amboceptor and Anticomplement Required. 



The following observations deal with the quantitative relations 

 existing between the amount of amboceptor and that of the anticom- 

 plement required to prevent haemolysis. In a number of cases we 

 determined the amount of anticomplement which just suffices to 

 prevent the solution of red blood-cells loaded with varying amounts 

 of amboceptor, when that amount of complement was present which 

 always just sufficed for complete solution. 



The majority of our experiments again refer to the solution of 

 sheep blood by an immune serum (derived from a goat) whose ambo- 

 ceptor is complemented by guinea-pig serum. This, it will be re- 

 called, is the case in which with large amounts of amboceptor the 

 complement required decreases considerably. For the anticomple- 

 ment we made use of the serum of a goat which had previously been 

 treated with repeated injections of rabbit serum. This serum, as 

 can be seen from a previous communication, does not only protect 

 against the complement of rabbit serum, but also against those of 

 guinea-pig serum. 



To begin, the amount of completing guinea-pig serum was deter- 

 mined which, with varying amounts of amboceptor, sufficed for 

 the complete solution of 1 cc. 5% sheep blood. After this the quan- 

 tity of anticomplement required in each instance to effect neutrali- 

 zation was determined, whereupon complement and anticomplement 

 were mixed and kept at 37 C. in an incubator for half an hour. 

 Blood and amboceptor were then added. Such an experiment is 

 reproduced in Table V. 



As shown in the table by the degree of haemolysis, the peculiar 

 behavior is observed that with small amounts of amboceptor 0.015 

 cc. anticomplement serum neutralize the complement of 0.05 in guinea- 

 pig serum, whereas with large amounts of amboceptor 0.35 cc. anti- 

 complement serum are required to neutralize 0.006 guinea-pig serum. 

 If we calculate the amount of complementing serum neutralized in 

 both cases by 1 cc. anticomplement serum, we find that in one case 

 it is 3.3 cc., in the other 0.017 cc. Hence when large amounts of ambo- 

 ceptor are employed the anticomplement acts 195 times weaker. 

 The required amount of anticomplement is therefore absolutely 

 dependent on the quantity of the amboceptor employed. This 

 becomes most evident by the fact that even with equal amounts of 



