The beta-configuration of the rhamnosidic linkage in Salmonella serogroups C2 and C3 lipopolysaccharide is important for the immunochemistry of the O-antigen 8.

Pairs of synthetic di- and trisaccharide-polyacrylamide (PAA) conjugates, isomers in configuration of the rhamnose residue and related to the sequence abequosyl-(alpha 1-3)-rhamnosyl-(beta 1-2)-mannose (ARM), found in Salmonella serogroup C2 (O-antigens 6,8) and C3 (O-antigens 8,20) lipopolysaccharides, have been used as coating antigens and inhibitors in enzyme immunoassay to evaluate the immunochemical importance of the beta-rhamnosidic linkage in the O-antigen 8. In each pair, the reaction with the factor O:6,8 serum was more pronounced for the synthetic antigen with the beta-rhamnosidic linkage. The ARM-PAA conjugate with the beta-rhamnosidic linkage was found to be 2000 fold more efficient as inhibitor of binding of the factor O:6,8 serum to the AR beta M-PAA conjugate as compared to the alpha-linked analogue. The discrepancy in immunochemical behaviour of the alpha and beta-rhamnose containing ARM oligosaccharides can be explained by conformational differences of the oligosaccharides. A slight cross-reactivity observed in the interaction of antiserum against abequosyl-(alpha 1-3)-mannose, representative of Salmonella O-antigen 4, coupled to BSA, with Salmonella O-factor 8 specific abequosyl-(alpha 1-3)-rhamnose containing conjugates is due to the common terminal immunodominant sugar, abequose.