Seventeen shigella strains of four subgroups: Sh. dysenteriae types-4, 6 and 7, Sh. flexneri types 1a, 2a, 2b, 3, 4a, 5, 6, variants X and Y, Sh. boydii types-1, 2, 5 and 6, and Sh. sonnei type-2 were grown on Medium D, described by Schlecht, S. & Westphal, O., and specific polysaccharide antigens were prepared from dried bacterial cells by the procedures I & II of Westphal, O. & Jann, K., and these were partly by Boivins' trichloroacetic acid extraction method. These were subsequently examined by immunoelectrophoresis. The antigens of all Shigella strains gave precipitin arcs, and immunoelectrophoretograms could be divided into two well-defined groups : IE groups I and II, according to the position of their precipitins formed on the arcs. The antigens of Sh. dysenteriae, Sh. boydii, Sh. sonnei and a few Sh. flexneri fell into the IE group I, which showed precipitin arcs both on the anodic side of the application basin and close to this. IE group II gave precipitin lines which were practically always located close to the application basin and included another Sh. flexneri which, however, belonged to IE group I. Extracts of Sh. sonnei and Sh, flexneri placed into IE group I contained a heat labile antigenic component which was destroyed or changed by heating at 100°C for 1 hour, although the entity was undetermined. It was difficult to separate the precipitin line of the group-specific antigen from the type-specific antigen by immunoelec-trophresis of the extracts examined. Cross reacting-antigens were observed between Sh. dysenteriae type-6, Sh. boydii type-6 and Sh. sonnei type-2, and one of these antigens was identified as an enterobacterial, common antigen of Kunin.
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