Granulocyte-activating mediators (GRAM): I. Generation by lipopolysaccharide-stimulated mononuclear cells

We undertook a study to determine whether cytokines exist which are responsible for the activation of polymorphonuclear neutrophilic granulocytes (PMN) besides the already well-known stimuli. Lucigenin-dependent chemiluminescence was used to measure human PMN activation. Addition of supernatants from mononuclear cells stimulated with bacterial lipopolysaccharide produced a long-lasting activation of granulocytes. Induction of chemiluminescence was dose-dependent and inhibitable by superoxide dismutase. Fractionation of mononuclear cells by adherence to plastic dishes or counterflow elutriation proved that monocytes were able to generate granulocyte-activating mediators (GRAM). Production of GRAM was dependent on the dose of the stimulus and appeared to be maximal after 24 h of incubation. Addition of cycloheximide resulted in significantly decreased release of GRAM. Partial characterization of the activity showed GRAM to be heat-labile and sensitive to trypsin, indicating a protein nature of GRAM. The activity fractionated into 2 distinct peaks, one corresponding to 60 kD and another below 10 kD. The interleukin 1 activity did not appear to co-fractionate with GRAM. Evidence presented suggests that the activity corresponds to factors unlikely to have been described previously.