AMBOCEPTOR AND COMPLEMENT 145 



the bacteria or their poisonous constituents to the cell. It differs 

 from the antitoxin, however, in that it has two affinities, one 

 for the complement and the other for the bacterial substance. 

 On account of the existence of the two affinities it is called an 

 amboeeptor. Some serums contain such amboceptors for certain 

 bacteria without previous immunization, hence the term immune 

 body is reserved for amboceptors developed by immunization. 



Amboeeptor and Complement. The function of the 

 amboeeptor 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 amboceptors to the bacteria gives them a 

 chemical affinity for complement. It is, therefore, an inter- 

 mediary body, uniting the complement to the bacterial protoplasm. 

 The complement is the substance that actually destroys the bac- 

 teria, 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 immuniza- 

 tion, 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 comple- 

 ment 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 ; indicating either that the complement 

 is not absolutely specific in its nature, or that quite the same com- 

 plement 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, however, that various 

 organs and cells may also produce complement. Its most 

 prominent characteristics are its extreme susceptibility to heat, 

 and the resemblance of its action to the action of enzymes. 1 

 Hektoen 2 found that it could be made to unite with Mg, Ca, 

 Ba, Sr, and SO 4 ions, which rendered the complement (for 

 typhoid bacilli and red corpuscles) inactive. Man waring 3 found 

 that these ions could be separated again from the complement 

 by simple chemical precipitation. 



According to the Ehrlich theory, complement, like toxins 

 and enzymes, possesses at least two groups : one, the hapto- 

 phore, with which it unites with the amboeeptor ; the other, the 

 toxophore (or zymophore, because of its enzyme-like action),which 



1 See Walker, Jour, of Physiol., 1906 (33), p. xxi. 

 a Trans. Chicago Path. Soc., 1903 (5), 303. 

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



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