BACTERIA, AMBOCEPTOR, AND COMPLEMENT 67 



ture of 68 to 70 C. The complement itself is incapable of combining 

 with the bacteria, whereas the amboceptor is readily anchored to the 

 organisms. This can be shown by treating serum with killed bac- 

 teria (of suitable kind) at a temperature of C., and subsequently 

 removing these by centrifugation. The absorption of the ambo- 

 ceptor is then shown by the fact that such serum is no longer capable 

 of causing the destruction of living organisms of the same order, 

 while the addition of such extracted but fresh serum to inactive 

 (heated), non-extracted serum will render this actively bactericidal. 

 The rationale of this will be readily understood by reference to 

 Fig. 1 and bearing in mind the relative thermostability of the 

 amboceptor as compared with the complement. 



FIG. 1 



Bacterium Amboceptor Complement 



Mechanism of Interaction between Bacteria, Amboceptor, and Comple- 

 ment. Much of our knowledge of the mechanism which is involved 

 in the interaction between bacteria, amboceptor, and complement has 

 been obtained from a study of the closely corresponding globulicidal 

 (hemolytic) properties which certain sera possess for red corpuscles 

 of animals of alien species. Working with washed corpuscles, the 

 compound character of the hemolysin, and the absorption of the 

 amboceptor by the cells, can be very well demonstrated as follows: 

 Red corpuscles from an animal of a suitable species are washed free 

 from serum with saline (by centrifugation), and then suspended for 

 a couple of hours in an actively hemolytic serum, the mixture being 

 kept at a temperature of from to 3 C. They are then thrown 

 down again by means of the centrifuge, when the supernatant fluid 

 is tested at body temperature, on the one hand against untreated 

 washed corpuscles, and on the other against those used in the 

 extraction. In the latter case hemolysis will result because the 

 corpuscles have absorbed the hemolytic amboceptor and are now 

 subjected to the action of the complement, union with which evi- 

 dently does not occur at the low temperature at which the extrac- 

 tion was carried out. In the case of the untreated corpuscles no 



