SALMONELLA ANTIGENS 107 



h, and group H antigens 1 and 2. From here on, however, we shall 

 be speaking of 5". ncivport as possessing O antigens 6 and 8. The 

 flagellar antigens will not come into the picture, because I do not 

 intend to discuss them further. 



The antigenic structure of the Salmonella has been studied in 

 great detail by Kauffman (1937) and White (1926) ; the classifica- 

 tion of these authors, based on the somatic and flagellar antigens, 

 is in common use. In general, the species of Salmonella are divided 

 into groups on the basis of similarity with respect to the O antigens, 

 and the species within a group are often differentiated according to 

 differences between their H antigens (Kauffmann, 1950, 1951). The 

 species have been arranged in groups designated A, B, C, etc., ac- 

 cording to similarities in the content of O antigens. All this, it should 

 be remembered, was done purely on the basis of serological evidence. 



Chemistry of the Polysaccharide Component 

 of Salmonella Antigens 



On hydrolysis, the Salmonella polysaccharides split into monosac- 

 charides and phosphoric acid. Chromatographic study of the sugars 

 shows that they represent a fairly complicated mixture ; a single 

 polysaccharide may consist of six to seven different sugars, in- 

 cluding hexosamines (glucosamine and galactosamine), heptoses, 

 hexoses, pentoses, and deoxy sugars (Davies, 1955; Mikulaszek 

 et al., 1956; Davies, 1960). The dideoxy sugars move faster on 

 chromatograms than the other sugars do, and their discovery, based 

 on this property, by Staub (1952) and Westphal (1952) was a new 

 fact of great immunochemical interest. They play a very important 

 role in the structure of the Salmonella antigens because : 



(a) Brief acid hydrolysis of the Salmonella lipoidpolysaccharides 

 always splits off these dideoxy sugars before significant amounts of 

 other sugars are released. This shows that the deoxy sugars are 

 terminal and acid labile in the branched polysaccharide structure. 

 It is known (see above, pp. 39-40) that the terminal groups play 

 a predominant role in hapten specificity. 



(b) When pathogenic "smooth" Salmonella forms change to the 

 nonpathogenic "rough" forms, the fast chromatographic sugar com- 

 ponents in hydrolysates of the antigens are missing, although the 

 endotoxic lipoid A component is still present. 



