Direct and indirect effects ofE. Coli lipopolysaccharide on isolated human polymorphonuclear granulocytes and mixed leukocytes

Polymorphonuclear neutrophil granulocytes (PMN) may contribute to the lung injury induced by nonpulmonary infections with gram-negative bacteria. The direct effect ofE. coli lipopolysaccharide (LPS) on isolated human PMN or mixed leukocytes (ML), as well as the priming effect of preincubating cells with LPS, was examined in assays measuring the maximal rate of oxygen consumption (OC), cell chemiluminescence (CHML), and aggregation (AGG). LPS, 1–10/ml, caused no acute response in PMN or ML suspended in Fisher's-HEPES medium with BSA (FHA), but increased both CHML and AGG of cells suspended in autologous plasma. Preincubation in FHA with LPS, 1g/ml, for more than 15 min increased the OC of PMN activated with zymosan-activated plasma (ZAP) orn-formyl-methionyl-leucyl-phenylalanine (FMLP) by more than 100%. A similar increase in the CHML of such cells was seen after FMLP, but not after ZAP. ZAP, however, primed the CHML response of the cells to subsequent activation with FMLP more than did preincubation with LPS. Previous exposure to both agents had an additive effect. Preincubation of PMN with LPS decreased the time interval from addition of phorbol myristate acetate (PMA) to peak OC response, but less so than previous activation with FMLP. Neither agent affected the maximal rate of OC after addition of PMA. LPS also increased the PMN aggregation induced by ZAP and FMLP, but not by PMA. Cells preincubated with LPS, 0.01 g/ml, increased their CHML in response to FMLP if suspended in Krebs-Ringer balanced salt solution, but not if suspended in FHA. Such preincubation had no effect on OC of similarly activated cells in any of the media.