Isolation and immunochemical characteristics of the immunodepressive substance from Escherichia coli.

A substance, inhibiting the production of haemolysins against sheep erythrocytes in mice was isolated from two non-pathogenic strains of E. coli, 020:K4 and M-17, by the methods of differential centrifugation and gel filtration. Spectrophotometric studies and chemical analysis have shown the isolated substance to be glycolipid. The immunodepressive substance is localized in the cytoplasm of the microbial cell. The isolated and partly purified immunodepressive substance did not contain any admixture of O-antigen (endotoxin) of the cell wall or of antigens giving cross reactions with sheep erythrocytes. The isolated substance exhibited weak antigenic properties and was not toxic for mice when administered in a dose of 2 mg (dry weight).