CHEMICAL CONSTITUENTS 285 



thetic carbohydrate-azoproteins were employed as antigens in the 

 production of immune rabbit serum. From the experiments, involv- 

 ing homologous precipitation and specific inhibition of precipita- 

 tion, confirmation was obtained of the view previously expressed by 

 Avery and Goebel that the immunological specificity of carbohy- 

 drates is determined by their stereochemical configuration, and 

 their data lent support to the further assumption that the intro- 

 duction of a simple chemical group, such as the acetyl radical, en- 

 dows a carbohydrate with a new and distinct specificity which is 

 determined by the chemical nature of the group thus introduced. 

 The differences exhibited by these two purely synthetic carbohy- 

 drate azoproteins accurately paralleled the differences in the sero- 

 logical specificity exhibited by the acetylated and deacetylated 

 polysaccharides of Type I Pneumococcus. 



Additional information concerning the A substance of Enders 

 was presented in the 1934 communication of Enders and Wu, 362 

 who prepared the A substance according to the procedure given by 

 Pappenheimer and Enders and the soluble specific substance by the 

 method of Heidelberger, Goebel, and Avery. The immune serum was 

 obtained by the repeated intravenous injection of rabbits with Type 

 I pneumococci in 0.3 per cent formalinized saline solution, and also 

 of suspensions of pneumococci killed by heating at 56° and 60°. 

 The immunological properties of the two polysaccharides were 

 then tested by the bactericidal method of Ward and by mouse-pro- 

 tection tests in which the mice had been treated with antipneumo- 

 coccic rabbit serum and also by active immunization with the A 

 substance. 



After the completion of the study, Enders and Wu announced 

 that the A substance possessed greater anti-opsonic action than 

 either the deacetylated carbohydrate obtained by boiling in alkali 

 or the SSS of Type I Pneumococcus prepared according to the 

 method of Heidelberger, Goebel, and Avery. The A substance 

 practically eliminated the opsonic titer of normal human serum — 

 an effect not observed with equivalent amounts of the deacetylated 



