[Antigens of Shigella dysenteriae serovars 3-7. IV. Immunochemical study of the exotoxin].

The exotoxins of Sh. dysenteriae, serovars 3 and 7, possess antigenic and serological properties and are characterized by the heterogeneous antigenic structure which distinctly differs from the structure of O-antigen in its immunochemical properties. These exotoxins consist of thermolabile and thermostable components. The thermolabile exotoxin fraction is a lethal toxin. The thermostable exotoxin fraction, obtained from the cultures of Sh. dysenteriae in the S-form, corresponds to O-antigen and forms an insignificant admixture in the concentrated exotoxins. The thermostable fraction of the exotoxins of S--R mutants differs from O-antigen by its serological specificity.