346 CYTOLYSINS 



as many of these as possible by preparing the serum from various animals 

 of the same and of different species. 



It will be understood, therefore, that the specific action of antibodies 

 of this order is not limited to the cells used in the immunizing process, 

 but extends to other cells that have receptors in common with these, 

 a condition that is analogous to group agglutinins and precipitins for 

 closely allied cells and bacteria or dissolved albumins. 



NATURAL OR NATIVE AMBOCEPTORS 



Difference Between a Normal and a Specific Immune Serum. Just 

 as small and varying amounts of native agglutinins and antitoxins may 

 be found in normal serums, so, in like manner, various native bacterio- 

 lytic and hemolytic amboceptors may be found. According to the side- 

 chain theory, these various amboceptors are normally attached to body- 

 cells, hence it is probable that a few are being continually swept off into 

 the blood-stream. In some instances the amount of a natural ambocep- 

 tor may be quite high; thus, for example, many human serums contain 

 relatively large amounts of antisheep hemolytic amboceptor. These 

 natural amboceptors will be considered more fully in the chapters on 

 Hemolysins and Bacteriolysins. 



The difference between a normal and an immune serum lies in the 

 fact that the normal serum contains a number of amboceptors in small 

 amounts, whereas the immune serum contains a greatly increased 

 amount of at least one amboceptor for a particular cell. As has been 

 shown by numerous investigators, this difference is not due to the 

 complements, as these are not increased during the process of immuni- 

 zation. Since the presence of an amboceptor cannot be demonstrated 

 unless complement is present, in testing a serum for an amboceptor we 

 must furnish sufficient complement to bring out the maximum activity 

 of the amboceptor. If the serum of a rabbit before and after immuniza- 

 tion is titrated with sheep erythrocytes, it may be found that the im- 

 mune serum contains from a hundred to many thousand times the 

 normal quantity of antisheep amboceptor. 



These facts bear a further practical relation to the treatment of 

 infectious diseases with bacteriolytic serums. Ordinarily, when we in- 

 ject an immune serum we furnish but one bactericidal substance, namely, 

 the bacteriolytic amboceptor, and no complement at all. If the pa- 

 tient's complement is decreased or at least insufficient to activate the 

 amboceptor furnished, lysis will not occur, and accordingly an increased 

 therapeutic effect may be secured by the injection simultaneously of 



