IL-4 production by human polymorphonuclear neutrophils

are phagocytic cells, able to secrete a large range of cytokines, including inflammatory cytokines, chemokines, as well as the Th1 cytokines interfer-on-g (IFN-g) 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 neutro-phils from normal donors contained low amounts of IL-4, which significantly increased upon culture with Brefeldin A (P < 0001). Immunostaining per-formed on cytospin preparations of normal granu-locytes 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 re-port here the presence within human PMN of in-tracellular IL-4, which can at least partly be re-leased under calcium ionophore stimulation. The relevance of this production of IL-4 by human PMN is discussed. J. Leukoc. Biol. 68: 125–130