[Immunochemical findings about the high molecular weight surface antigens of Shigella sonnei]

The authors studied immunochemical properties of the high molecular fraction of surface soluble antigens obtained by extraction with salt solutions from Sh. sonnei (virulent strain 1041) dried with acetone. The high molecular fraction was isolated by gel-filtration on Sepharose-4B. Along with the O-somatic antigen, this fraction contained thermostable and thermolabile antigens resistant to trypsin and RNA-ase treatment, and also protein-containing antigens disintegrated by trypsin. In difference from the O-somatic antigen, one of the thermostable components was completely precipitated with 50% alcohol.