AMBOCEPTOR A^D COMPLEMENT 211 



It is believed tliat the action of these substances is as follows : The 

 immune body is, like antitoxin, a cell receptor which unites the bac- 

 teria to the cell. It differs from the antitoxin, however, in that it 

 has two affinities, one for the complement and the other for the bac- 

 terial substance. On account of the existence of the two affinities it 

 is called an amboceptor. Some serums contain such amboceptors for 

 certain bacteria without previous immunization, hence the term im- 

 mune amboceptor is reserved for amboceptors developed by immuniza- 

 tion. 



Amboceptor and Complement. — The function of the amboceptor 

 is to unite the bacterial protoplasm, to which it is attached by one 

 affinity, to the complement which it holds by its other affinity, or, to 

 put it in a more strictly chemical way, the addition of the ambocep- 

 tors to the bacteria gives them a chemical affinity for complement. 

 It is, therefore, an intermediary body, uniting the complement to the 

 bacterial protoplasm. The complement ^ is the substance that actually 

 destroys the bacteria, in which respect, as well as in its susceptibility 

 to heat, it resembles the enzymes. Complement is present in normal 

 serums, and, as it is not increased in amount during immunization, 

 it may not be sufficient to satisfy all the amboceptors, hence it may 

 be impossible to secure marked bactericidal effects even when many 

 amboceptors have been formed. If the complement in an immune 

 serum has been destroyed by heating, it may be replaced by adding 

 normal serum from another animal, even of some other species; indi- 

 cating either that the complement is not absolutely specific in its 

 nature, or that quite the same complement may be present in the 

 blood of many different animals. The origin of the complement is 

 unknown, but it has been urged that the leucocytes are an important 

 source of this substance, if not its chief one ; ^^ there is evidence, how- 

 ever, that various organs and cells may also produce complement.^*^ 

 Its most important characteristics are its extreme susceptibility to 

 heat, and the resemblance of its action to the action of enzymes.'* 

 Hektoen ^ found that it could be made to unite vsdth Mg, Ca, Ba, Sr, 

 and SO^ ions, which rendered the complement (for typhoid bacilli and 

 red corpuscles) inactive. ]\Ianwaring '^ found that these ions could be 

 separated again from the complement by simple chemical precipita- 



a similar complex structure, but quite distinct from the serum bacti.Tiolvsins. 

 (See Kling, Zeit. Immunitat., 1910 (7), 1). 



3 Review and bibliography by Noguchi, Biochem. Zeit., 1907 (6), 327. 



3a Cholera antiserum will produce the Pfeiffer phenomenon of lysis of cholera 

 vibrios in animals made leucocyte-free with thorium, showing that the presence 

 of the leucocytes themselves is not essential. (Lippmann, Zeit. Immunitiit., 

 1915 (24), 107.) 



3b See Dick, Jour. Infect. Dis., 1913 (12), 111; and Lippmann and Plesch, 

 Zeit. Immunitiit.. 1913 (17), 54S. 



4 See Walker, Jour, of Phvsiol.. 1906 (33), p. xxi. 



5 Trans. Chicago Path. Soe., 1903 (5), 303. 



6 Jour. Infectious Diseases, 1904 (1), 112. 



