[Immunodepressive activity of cell fractions of Escherichia coli O138:K81:H19].

A soluble cell fraction (cytosol), an O-antigen (endotoxin), and an unsoluble cell ingredient were isolated from a 24-hour culture of Escherichia coli O138:K81:H19. Their immunosuppressive action was determined by using the tuberculin test and the survival rate of the allographts. It was found that: 1. Cytosol appears to be a slightly toxic preparation with well expressed immunosuppressive action. 2. The endotoxin is highly toxic, producing the same effect as cytosol. 3. The unsoluble cell ingredient is a comparatively toxic preparation, producing an undependable immunosuppressive effect. Discussed is the mechanism of the immunosuppressive activity of the investigated subcellular fractions. It believed to be due to a certain injurious action on the function of the T-cells.