Isolation of a macrophage-like cell line defective in binding of lipopolysaccharide. Influence of serum and lipopolysaccharide chain length on macrophage activation.

A mutant cell line (J7.DEF.3) derived from murine macrophage-like J774.1 cells, was isolated on the basis of defective specific 125I-labeled LPS-binding in the presence of serum. Although J7.DEF.3 cells still respond to LPS in inducing TNF-alpha release and nitric oxide (NO) formation, these cells nevertheless showed significantly decreased responsiveness to LPS relative to the J774.1 parent. Under serum-free conditions, no differences between J774.1 and J7.DEF.3 cells in response to LPS were observed. The time kinetics of responsiveness to LPS also showed a delay in the onset of TNF-alpha release and NO formation in the mutant cells relative to parent cells. Importantly, this decrease in responsiveness to LPS relative to parental cells was dependent on the length of the polysaccharide portion of LPS. The defect in the mutant cells has been shown to be specific for LPS, in that these cells respond to heat-killed Listeria monocytogenes and to zymosan to a similar extent as do the parental cells. Collectively these results suggest that the defect in the J7.DEF.3 mutant cells may be related to a cellular LPS-binding molecule that, in turn, may depend upon an LPS-binding serum component.