INTERFERON-GAMMA AND POLYUNSATURATED FATTY-ACIDS INCREASE THE BINDINGOF LIPOPOLYSACCHARIDE TO MACROPHAGES

We have previously shown that interferon-gamma (IFN-gamma) increases t he polyunsaturated fatty acid content of membrane phospholipids in cel ls that were sensitive to endotoxin. In this study, IFN-gamma was foun d to stimulate the binding of endotoxin to the murine macrophage cell line J774.2 and the human monocyte cell line U937. Interferon-gamma-ac tivated J774.2 cells showed a 66% increase in fluoresceine isothiocyan ate (FITC) labelled LPS binding (P < 0.0005 vs control cells) and a 49 % increase in tritium labelled LPS binding (P < 0.0001 vs control cell s). Interferon-gamma also induced a 35% increase in binding of FITC-LP S in U937 cells (P < 0.0001 vs control cells). In contrast, pretreatme nt of J774.2 cells with interferon-beta (IFN-beta) had no effect on bi nding of FITC-LPS. Preincubation with exogenously supplied polyunsatur ated fatty acids, linoleic and arachidonic acids, resulted in increase s of 74% and 69% in FITC-LPS binding, respectively (both P < 0.0005 vs control cells). On the other hand, pretreatment with the saturated fa tty acid, palmitic acid, had no effect on FITC-LPS binding. We propose that IFN-gamma-induced changes in the membrane phospholipid fatty aci d composition of macrophage-like cells influence the binding of endoto xin.