INTERLEUKIN–13 AND INTERLEUKIN–4 ACT AS INTERLEUKIN–6 INDUCERS IN HUMAN MICROGLIAL CELLS

Abstract The effect of interleukin 4 (IL–4) and IL–13 on IL–6 and IL–1β production by human embry-onic microglial cells and human peripheral blood monocyte cells (PBMC) was compared. IL–4 or IL–13 increase intra-cellular IL–6 mRNA and IL–6 titres in supernatants of microglial cells whereas they decreased IL–6 production by PBMC tested in the same conditions. IL–4 and IL–13 increased also IL–1β production by human microglial cells. Stimulations associating IL–4 or IL–13 and IL–1b had an additive effect on IL–6 production by microglial cells, whereas, in the same conditions, an inhibitory effect was observed in PBMC. In contrast, dexamethasone downregulated IL–6 production by microglial cells and PBMC. Finally, IL–1 receptor (IL–1r) type 1 and IL–1r type 2 were detected on human microglial cells but it was demonstrated that IL–13 and IL–4 acted as IL–6 inducers in human microglial cells independently of the IL–1/IL–1r pathway.