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, Similar
ly to eosinophils, freshly isolated neutrophils from normal donors containe
d low amounts of IL-4, which significantly increased upon culture with Bref
eldin A (P < 0001), Immunostaining performed on cytospin preparations of no
rmal granulocytes confirmed the presence of intracellular IL-4. Using a hig
hly sensitive ELISA, the levels of IL-4 secreted by cultured PMN and periph
eral blood mononuclear cells (PBMC) Tc ere compared, PBMC secrete up to 60
times more IL-4 as PMN but, in the presence of calcium ionophore, only PMN
shore-ed 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 stimula
tion. The relevance of this production of IL-4 by human PMN is discussed.