Tumor Necrosis Factor‐inducing Activities of Lipid A Preparations from Pseudomonas diminuta and Pseudomonas vesicularis

Tumor necrosis factor (TNP)‐inducing activities of lipid A preparations from P. diminuta and P. vesicularis, which contain mainly 2 mol of 2,3‐diamino‐2,3‐dideoxy‐D‐glucose and 1 mol of nonglycosidic phosphate as the backbone component and have partly different fatty acid compositions, were examined. TNF was induced by injecting various lipid A fractions into mice that had previously been sensitized with Mycobacterium bovis BCG vaccine. A major component of lipid A of both strains, referred to as A3 fraction, exhibited stronger TNF‐inducing activity than A2 fraction having incomplete acyl residues. The removal of ester‐linked fatty acyl groups by mild hydrazinolysis of the P. diminuta lipid A results in a marked decrease of the activity. These results suggest that the structure of the hydrophobic part, including the amide‐linked acyloxyacyl group(s), of the lipid A molecule play an important role in inducing TNF in the sera of mice.