The serological specificity of Salmonellae (O-specificity) is mediated by oligosaccharide subunits (repeating units) of the species-specific cell wall polysaccharides. With S. illinois (O-specificities 3, 15 and 34 of the Kauffmann-White scheme) as a representative example, it was possible to achieve the coupling of a complete repeating unit of that kind (in the case of S. illinois a tetrasaccharide) to protein, thus converting it into an artificial antigen. The repeating tetrasaccharide of the O-specific S. illinois polysaccharide has been obtained by partial acid hydrolysis of the O-specific S. illinois lipopolysaccharide and has the following structure with rhamnose as the reducing terminal sugar: In a reaction of this tetrasaccharide (TSill) with o-phenylenediamine and m-nitrophenylhydrazine and its subsequent reduction, TSill-illl-(3-amino-phenyl)-flavazole was prepared, which was then coupled to edestin by means of the azo-method. Antisera obtained after immunization of rabbits with the TSill-illl-(3-azophenyl)-flavazole-edestin conjugate contained TSill-specific antibodies, as shown by agglutination of S. illinois bacteria as test antigen (titers up to 1:2500). The specificity of these antibodies was tested in detail by cross-agglutination with various bacterial strains. These antibodies are predominantly directed against the non-reducing end group Glc Gal (Man) (O-factor 34), and only to a slight extent against the internal groupings' Gal Man (O-factor 15) and Man (Rha) (O-factor 3). The serum antibodies did not show cross-reactions with O-factor 122, which differs from O-factor 34 in the configuration of the Gal Man-linkage (122 :α-glycosidic, 34:β-glycosidic). Thus, by immunization of rabbits with a TSill-illl-(3-azophenyl)-flavazole edestin conjugate, a largely factor-specific (anti-34) antiserum was obtained.
