The role of the structural parts of bacterial lipopolysaccharide in its direct immunosuppressive activity]

The direct immunosuppressive activity of lipopolysaccharides (LPS) and their structural parts (O-chains, R-core, lipid A), obtained from Salmonella, Pseudomonas and Burkholderia, was studied. LPS preparations were extracted by the phenol-water method. Structural parts of LPS were obtained by acetic acid hydrolysis and gel filtration. The study demonstrated that all these preparations, when injected intraperitoneally into mice, did not affect the level of delayed-type hypersensitivity (DTH) to the test antigen in the animals. After redox treatment all LPS preparations became capable of suppressing DTH. After redox treatment such immunosuppressive activity could be observed in lipid A, while O-specific chains and R-core remained inactive. After phenol treatment immunosuppressive activity disappeared. Chemical groups capable of activation were likely to be located in lipid A or in lipid A-associated protein.