Interleukin-6 Production by Human Neutrophils After Fc-Receptor Cross-Linking or Exposure to Granulocyte Colony-Stimulating Factor

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Abstract
Polymorphonuclear neutrophils (PMNs) are essential effector cells in host defense and tissue inflammatory responses. These responses may be initiated after cross-linking of cell surface Fc receptors that bind the constant portion of IgG (FcγR). We evaluated the effect of cross-linking FcγRI or FcγRII on interleukin-6 (IL-6) production by purified PMNs from normal donors or from patients being treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF). In PMNs from normal donors, IL-6 mRNA was detected by reverse transcriptase-polymerase chain reaction only after FcγRI or FcγRII cross-linking. We also found that IL-6 mRNA could be detected in PMNs after either in vitro or in vivo rhG-CSF treatment in the absence of FcγR cross-linking. IL-6 protein was found to be produced intracellularly and secreted by PMNs after cross-linking FcγRI or FcγRII or after rhG-CSF stimulation. Cross-linking FcγRI or FcγRII on PMNs from patients treated with rhG-CSF resulted in a synergistic increase in IL-6 secretion. Upregulation of IL-6 production by PMNs after rhG-CSF treatment may contribute to a clinical engraftment syndrome that occurs during periods of rapid increase in PMN numbers in patients receiving rhG-CSF.