[Somatic antigens of Shigella and Escherichia coli. Determination of the structure of O-specific polysaccharide from Shigella boydii type 12 and its serological properties compared with the O-specific polysaccharide from Escherichia coli].

The structure of the O-specific polysaccharide of the somatic antigen (lipopolysaccharide) of Shigella boydii, type 12, was established by 1H- and 13C-NMR, methylation analysis and partial acid hydrolysis methods. The polysaccharide consists of pentasaccharide repeating units of the following structure: (formula; see text) The amount of O-acetyl groups was far less than stoichiometric, only about 2 for 3-4 repeating units. Nevertheless, the results of serological studies revealed 3-O-acetyl-alpha-L-rhamnose residue to be the major immunodominant group. In spite of the presence of similar trisaccharide fragments, the lipopolysaccharide and polysaccharide from Shigella boydii type 12 gave no crossreaction with lipopolysaccharide and polysaccharide from Escherichia coli 07. The possible reasons of the absence of serological relatedness between the Sh. boydii, type 12, and E. coli 07 cells were discussed.