Antibiotic — Neutrophil Interactions Studied by Phase Partitioning

Abstract

In an investigation of phase-forming polymers concerning their stimulatory effect on neutrophils (PMNLs), a number of dextrans were found to stimulate neutrophil oxidative metabolism as detected by nitroblue tetrazolium (NBT) reduction [1]. This effect was removed by addition of polymyxin B sulphate — a cyclic polypeptide antibiotic which binds to lipid A [2] and neutralises many of the biological effects of bacterial endotoxin [3,4]. This indicated that contaminating bacterial lipopolysaccharide (LPS) is present in some batches of dextran, but can be removed by addition of polymyxin B. Unfortunately, we observed that polymyxin B also enhanced the phagocytic capacity of the neutrophil. Consequently its incorporation into the phase reagents as a means of neutralising the effects of LPS is precluded. These observations prompted us to examine the surface properties of neutrophils in the presence and absence of polymyxin B by single step partitioning in charge-sensitive and non-charge-sensitive phase systems and the contribution of these surface properties to the observed increase in neutrophil phagocytosis.