XIX. ON THE RELATIONS OF SENSITIZERS TO 



ALEXIN* 



By DRS. J. BORDET and F. P. GAY. 



Those who have made a study of hemolysis hold very divergent 

 opinions as to the relations between the susceptible corpuscle and 

 the substances that affect it, namely, the sensitizer (amboceptor) 

 and the alexin (complement). It is well known that the blood 

 corpuscles fix the sensitizer (Ehrlich and Morgenroth), and that 

 corpuscles so modified have the new property of energetically 

 absorbing all the alexin from the surrounding fluid. (Bordet.) 

 It is evident, then, from these facts that the sensitizer acts as an 

 intermediary agent in bringing about the union between the sen- 

 sitive cell and the toxic substance or alexin. 



It is perfectly evident that there is some not well understood 

 substance in the red blood cell which unites and forms a complex 

 with the sensitizer. This much and no more has been experimen- 

 tally demonstrated ; the intimate nature of the reaction is unknown. 



It is scarcely profitable to explain this simple fact in any elaborate 

 fashion. To say that the corpuscle receives and holds the sen- 

 sitizer by means of a "receptor," or that the sensitizer combines with 

 such a receptor because it has a combining cytophilic group, is to 

 pretend to a knowledge not yet obtained. We may content our- 

 selves by saying that a complex is formed. 



But how does this complex (sensitizer-corpuscle) fix alexin? 

 To which constituent of the complex is the affinity for this sub- 

 stance due? It is certainly not the corpuscle itself, for we find that 

 normal unsensitized corpuscles do not take up alexin. Is it, then, 

 the sensitizer, or is it the combination of the two, that shows an 

 avidity for alexin that neither one of its constituents alone possesses? 



Both hypotheses have been suggested. The first one, namely, 



* Sur les relations des sensibilisatrices avec l'alexine. Annales de l'lnstitut 

 Pasteur, XX, 1906, 467. 



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