Activation of neutrophil function by recombinant human granulocyte-macrophage colony-stimulating factor and modulation of its action by alpha-2-macroglobulin

Abstract

Neutrophils play an important role in inflammation as they are the predominant cell type at the sites of infection. The function of these cells can be activated in vitro by a number of agents. Granulocyte colony-stimulating factor (G-CSF) and gradulocyte-macrophage colony-stimulating factor (GM-CSF) are known to have an influence on neutrophil function. G-CSF and GM-CSF belong to a family of cytokines known as colony-stimulating factors (CSFs). CSFs are a group of cell-derived products responsible for the proliferation and differentiation of progenitor cells. These factors are available in large amounts through recombinant DNA techniques. Superoxide species are important for oxygen-dependent mechanisms by which neutrophils can kill certain microorganisms. In this research recombinant human G-CSF (rhG-CSF) and recombinant human GM-CSF (rhGM-CSF) were used to activate human neutrophils to release superoxide anion.Recombinant human GM-CSF at 5 to 500 U/ml greatly enhanced the production of superoxide anion by neutrophils stimulated by N-formyl-methionyl-leucyl-phenylalanine (FMLP). However, rhG-CSF at 50 U/ml did not show this enhancement. In addition, rhGM-CSF alone at 50 U/ml stimulated superoxie production by neutrophils in a time-dependent manner. The modulation of neutrophil function by alpha-2-macroglobulin (alpha-2M), which is the only plasma inhibitor of a number of proteases, was also studied. The binding of some cytokines to alpha-2M has been shown by previous studies to regulate certain immunological functions. Recombiant human GM-CSF and native alpha-2M alone and in combination stimulated in significant increase of superoxide production. In contrast, the fast form of alpha-2M, modified by either trypsin or ammonium sulphate, inhibited the release of superoxide anion by neutrophils. These findings reflect that rhGM-CSF could activate neutrophil function relevent to resistance to infection and that alpha-2M may modulate the action of neutrophils.