The role of O-antigen polysaccharide in the activation of neutrophils by lipopolysaccharides of Salmonella species.

Activation of neutrophils by lipid A, O-antigen polysaccharides (PS) and smooth lipopolysaccharides (LPS) isolated from Salmonella choleraesuis (O-6,7) and Salmonella typhimurium (O-4,5,12) was investigated. The methods used were assays for lysozyme release and for nitroblue tetrazolium (NBT) reduction which measures the level of oxidative metabolism of neutrophils. LPS from both species stimulated neutrophils to the same extent in the presence of autologous plasma. In the absence of plasma only the O-6,7 LPS activated neutrophils. Lipid A or PS isolated from both LPS either did not activate neutrophils or did so only at very high concentrations when tested in the presence of plasma; in the absence of plasma no activation occurred. The data indicate that both PS and lipid A segments of LPS are required for activation of neutrophils by LPS. We also deduce that plasma, probably complement, is required for the interaction of some LPS, e.g. O-4,5,12 with neutrophils whereas other LPS, e.g. O-6,7 can interact directly and activate neutrophils.