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Development and Identification of a Novel Subpopulation of Human Neutrophil-derived Giant Phagocytes In Vitro
Published on: January 25, 2017
IL-4 production by human polymorphonuclear neutrophils
E Brandt1, G Woerly, A B Younes
1Unité INSERM U167, Institut Pasteur, Lille, France.
Abstract:
Polymorphonuclear neutrophils (PMN) are phagocytic cells, able to secrete a large range of cytokines, including inflammatory cytokines, chemokines, as well as the Th1 cytokines interferon-gamma (IFN-gamma) and interleukin (IL)-12. Although PMN do not seem to express IL-10 and IL-13, no information exists on the ability of PMN to produce IL-4. Therefore intracellular flow cytometry was performed in the presence or absence of Brefeldin A. Similarly to eosinophils, freshly isolated neutrophils from normal donors contained low amounts of IL-4, which significantly increased upon culture with Brefeldin A (P < 0001). Immunostaining performed on cytospin preparations of normal granulocytes confirmed the presence of intracellular IL-4. Using a highly sensitive ELISA, the levels of IL-4 secreted by cultured PMN and peripheral blood mononuclear cells (PBMC) were compared. PBMC secrete up to 60 times more IL-4 as PMN but, in the presence of calcium ionophore, only PMN showed a slight but significant increase in IL-4 secretion (P < 0.05). In conclusion, we report here the presence within human PMN of intracellular IL-4, which can at least partly be released under calcium ionophore stimulation. The relevance of this production of IL-4 by human PMN is discussed.
Insights
Human neutrophils (PMN) possess intracellular interleukin-4 (IL-4), a cytokine previously not known to be produced by these cells. This intracellular IL-4 can be released upon specific stimulation, suggesting a novel role for PMN in immune responses.
Area of Science:
- Immunology
- Cell Biology
- Cytokine Research
Background:
- Polymorphonuclear neutrophils (PMN) are key phagocytic immune cells.
- PMN secrete various cytokines, including inflammatory mediators and Th1 cytokines like IFN-gamma and IL-12.
- The production of IL-4 by PMN was previously uncharacterized.
Purpose of the Study:
- To investigate the potential of human PMN to produce interleukin-4 (IL-4).
- To characterize the intracellular presence and release of IL-4 from PMN.
Main Methods:
- Intracellular flow cytometry was performed on neutrophils, with and without Brefeldin A.
- Immunostaining was used to confirm intracellular IL-4 in granulocytes.
- Highly sensitive ELISA compared IL-4 secretion by PMN and peripheral blood mononuclear cells (PBMC).
Main Results:
- Freshly isolated neutrophils contained low intracellular IL-4, which significantly increased after culture with Brefeldin A.
- Immunostaining confirmed the presence of intracellular IL-4 in human granulocytes.
- While PBMC secreted substantially more IL-4, PMN showed a significant increase in IL-4 secretion upon calcium ionophore stimulation.
Conclusions:
- Human PMN contain intracellular IL-4.
- This intracellular IL-4 can be partially released following calcium ionophore stimulation.
- The findings suggest a potential, previously unrecognized role for PMN in IL-4 production and immune modulation.
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