Studies in immunochemistry

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Abstract
The antigenic complex of Shigella dysenteriae is soluble in conc. (90%) solns. of phenol. In phenol soln. the complex is largely dissociated into its protein and polysaccharide components which can then be isolated in a free state by dialysis of the phenol soln. The antigenic complex is partly dissociated in aqueous alkaline soln. and the components can be separated by repeated fractionation of the antigenic complex from alkaline soln. by alcohol. The protein-free polysaccharide component prepd. by either method fails to induce the formation of specific "Shiga" agglutinins or precipitins in the rabbit. Some evidence is given for the view that the acidic protein component previously descr. by the term "polypeptide-like" is a conjugated protein. It is devoid of antigenicity as measured by the production of "Shiga" immune-body, but can be recombined in aqueous soln. with undegraded "Shiga" specific polysaccharide to form a powerful antigen. The protein isolated from the antigenic complex by phenol or alkali dissociation is amphoteric and has a higher N content and optical rotation than the conjugated protein. The simple amphoteric protein can also be isolated directly from the conjugated protein component of the antigenic complex. The simple protein does not form an antigenic complex when mixed with "Shiga" polysaccharide in aqueous solution. The extraction of a "smooth" culture of Shigella dysenteriae with 90% phenol yields the characteristic water-soluble antigenic complex and about an equal amt. of the non-specific, water-insoluble simple protein. Similar extraction of the corresponding "rough" variant yields no antigenic material but a considerable quantity of the simple protein.