Studies in immunochemistry. 15. The specific polysaccharide of the dominant ‘O’ somatic antigen of Shigella dysenteriae

Abstract

Three polysaccharide preparations were obtained from cultures of "Smooth" S. dysenteriae. Each material has the specificity of the dominant "O" somatic antigen of the homologous organism. The materials showed no evidence of inhomogeneity on ultracentrlfugal and electro-phoretic analysis at acid and alkaline pH. The degraded polysaccharide haptene,[[alpha]] [image] + 98[degree]; N, 1.9%, obtained from the isolated antigenic protein-polysaccharide complex contains acetylglucosamine (27.5%), rhamnose (33%) and galactose (27%). No P was present. Molecular weight 25,000 - 28,000 by end-group assay and 26,000 by sedimentation and diffusion measurements, showing the identity of the chemical and physical units. The degraded polysaccharide is neither toxic nor antigenic, but is pyrogenic in relatively large doses (2-5 [mu]g/kg). The undegraded polysaccharide, [[alpha]] [image] - 94[degree]; N, 2.2%, extracted from the organisms with diethylene glycordiffered from the degraded material in containing a few per cent of amino acids, and in having a molecular weight of the order of one million by sedimentation and diffusion measurements. The material is poorly toxic (mouse LD50, 400 [mu]g), is weakly antigenic and is less active as pyrogen (0.05 [mu]g/kg) than the lipopolysaccharide or complete antigen. The lipopolysaccharide, [[alpha]] [image] + 95[degree]; N, 2.04%; P, 0.8%, extracted from the isolated antigenic protein-polysaccharide complex with phenol contains about 7% of chloroform-soluble, ether-insoluble phospholipid. The lipopolysaccharide is of very large particle size, is toxic (mouse LD50, 80ug) and is a strong heterophile (Forssman) antigen, but weakly active in inducing the formation of specific agglutinins and precipitins in rabbit. The material is also a very powerful pyrogen, active at 0.002 [mu]g/kg in the rabbit.