INTERACTIONS OF LIPOPOLYSACCHARIDE WITH NEUTROPHILS IN BLOOD VIA CD14

The functional characteristics of neutrophils are exceedingly sensitiv e to physiological conditions as well as the details of isolation. Exp osure to lipopolysaccharide (LPS) or even contamination of the isolati ng media with traces of LPS is known to play an important role in regu lating cell function and expression of receptors. Because of the suspe cted role of CD14 as a receptor for LPS, we used anti-CD14 monoclonal antibodies both to identify CD14 in the cell surface of polymorphonucl ear leukocytes and to inhibit functional changes elicited by LPS. Cyto metric techniques were used to investigate the regulation of CD14 and CR3 on the neutrophil cell surface in whole blood to minimize any effe cts of isolation. In whole blood neutrophils express low levels of for myl peptide receptor, CD14, and CR3, which increase substantially in r esponse to formyl peptide and LPS. The increases in CR3 and CD14 occur red in parallel and were independent of protein synthesis and tumor ne crosis factor (TNF) production. The increase in CR3 was inhibited by a ntibodies MY4, 3C10, and 28C5 against CD14. These findings are consist ent with the notion that in blood the observed receptor up-regulation is in direct response to the action of LPS on neutrophils through CD14 and does not require products from macrophages such as TNF or the pro duction of C5a from the plasma.