226 THE ANTIGEN-ANTIBODY REACTIONS 



A p sents the complement, with its 



haptophore group h, by which it 



.'C ■// jC^^ is attached to the complemento- 



^- / ^\Vi ,--S philic group of the amboceptor, 



^W^" ""^ >-C^ ^VP^^^^^Qqi ^^^ 6 its ergophore group, in 



/ ^T^^ ^/^ \ virtue of which it brings about 



I R.C 1 ,'R ^5^ f{Q j lysis of the red cell, when united 



V y j=^^). J to it by the hsemolytic ambocep- 



>— ^ '''' ^-_^ tor. 



f)""ty Bordet's conception of the 



jiS.:^l^ action of the hsemolytic antibody, 



M —t which he refers to as the " svh- 



FiG. 40. stance sensibilisatrice," or sensi- 



tizer, is essentially different. He 

 denies that the sensitizer acts as a link between the red cell and the complement, 

 or that the complement ever unites with the sensitizer as such. He regards the 

 combining affinities of the haemolysin as being directed entirely upon the red cell. 

 The complement, in his view, unites not with the haemolysin, but with the com- 

 plex, red cell + haemolysin, or, to put it in another way, with the red cell as altered 

 by union with the haemolysin. Bordet's conception may be represented diagram- 

 matically in Fig. 4Ub. R.C. represents the red cell ; S the sensitizer or haemolysin, 

 which has united with the red cell, and altered the physical conditions at the sur- 

 face ; and C the complement, uniting with the red cell which has been so altered. 

 It will be seen that the controversy can be narrowed down to the question : 

 what evidence is there for the existence of a complementophilic group of the 

 haemolysin ? We have not space to present all the experimental data which have 

 been advanced by each side in turn, nor the arguments which have been based 

 upon them. It may, we think, be safely asserted that Ehrlich and his supporters 

 have, in this respect, failed to substantiate their position, and that the weight of 

 evidence strongly upholds Bordet's view. 



The quantitative aspects of the union between red cells and haemolysin have been studied 

 by many observers, and the results recorded have been of the same general kind as those 

 observed with mixtures of soluble antigens and the corresponding antibodies, or with 

 bacteria and their homologous agglutinins. They are not compatible with the view that 

 red cells and hsemolysin imite in constant proportions, in a firm chemical union. They 

 are compatible with the view that the union obeys the laws of an adsorption process — for 

 instance, Bordet was able to demonstrate a reaction analogous to the Danysz phenomenon. 

 They show (see Muir 1909) that the red-ceU-hsemolysin compound can be dissociated 

 under certain conditions, though the dissociation is not of the type that occurs on 

 simple dilution of a dissociable chemical compound. There is, indeed, no reason to 

 suppose that the laws that determine the union of a hsemolysin with the specific antigenic 

 components of a red cell differ in any way from those that determine the union of 

 precipitins or agglutinins with their corresponding antigens. 



Not all the antigenic groups on the surface of the red cell appear to take part m the 

 sensitization of the cell to the action of complement. Heidelberger, Weil and Treflfers 

 (1941), calculate that, in a red cell suspension sensitized by one minimal hsemolytic dose 

 of hsemolysin (see below), at most only 14 per cent, of each cell surface is occupied by 

 antibody. A figure of the same order, 6 per cent., was estimated by Haurowitz and 

 Yenson (1943). 



The effect of electrolytes and hydrogen-ion concentration on the union of hsemolysin 

 with red cells has been referred to on p. 211, m relation to the imion of agglutinins with 



