XVII. THE FIXATION OF ALEXINS BY SPECIFIC 

 SERUM PRECIPITATES.* 



BY FREDERICK P. GAY, M.D. 



We possess already a wealth of experimental detail relative to 

 the specific immune bodies formed in the sera of animals injected 

 either with simple cells or with such complex fluids as defibrinated 

 blood or blood serum. Among the best known of these immune 

 bodies are the specific hemolysins and bacteriolysins, the activities 

 of which have been most fruitfully studied. We know, for example, 

 that a given hemolytic immune body (substance sensibilisatrice, 

 amboceptor) formed after the injection of foreign red blood cells 

 has two important properties, namely, the property of sensitizing 

 the causative cell in such a manner as to allow it to be destroyed by 

 the alexin (complement) of various fresh normal sera; and secondly, 

 the power, when it has formed a complex with the causative cell, 

 of fixing an alexin. This second property is perhaps the more 

 important, since the alexin can often be shown to have been absorbed 

 by the cell-immune-body complex even when the cell itself is not 

 destroyed. Indeed, this absorption of alexin has given the means 

 of determining the existence of sensitizing substances where they 

 might not otherwise have been shown to exist. Bordet and 

 Gengouj have shown that the majority of antimicrobial sera con- 

 tain "substances sensibilisatrices " that absorb alexin in instances 

 where destruction of the specific bacteria is not produced, ami 

 GengouJ has further shown that the injection of certain albuminoids 

 may likewise give rise to specific sensitizing sera which may form 

 with the causative substances mixtures that absorb alexin. 



* Centralblatt fur Bakt., I Abt., Orig. XXIX, 1905, 603. 

 t Bordet and Gengou, see p. 217. 

 J Gengou, see p. 241. 



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