P084 Bioactive lipids at the surface of stimulated T cells induce cytokine production in human monocytes

Imbalance in cytokine homeostasis plays an important part in the pathogenesis of chronic inflammatory diseases such as multiple sclerosis and rheumatoid arthritis. Stimulated T cells exert a pathological effect through direct cellular contact with monocytes/macrophages, inducing a massive up-regulation of IL-1β and TNF in the latter cells. This mechanism that is likely to be relevant to chronic/sterile inflammation is specifically inhibited by high-density lipoproteins (HDL). Here we determine that cytokine induction is due to lipids present in membranes of stimulated T cells. Chloroform:methanol or methyl-ter-butylether extraction of lipids from membranes isolated from PMA/PHA-stimulated and unstimulated HUT-78 cells and peripheral blood T lymphocytes. Methylamine treatment. Mass spectrometry analysis of total lipids. Induction of cytokine production/expression in isolated human blood monocytes. Total lipids isolated from membranes of stimulated HUT-78 cells and T lymphocytes induced IL-1β, sIL-1Ra and TNF production in monocytes, whereas aqueous fraction was inactive. Pro-inflammatory cytokine production was inhibited in the presence of HDL. These results indicated that lipids were the active factors that induced cytokine production upon direct cellular contact activation of monocytes by stimulated T cells. The activity was abolished when lipids were treated with methylamine suggesting that sphingolipids were not involved in monocyte activation. Comparison of mass spectrometry profiles of total lipids from membranes of stimulated and unstimulated HUT-78 cells suggested the involvement of lysophospholipids in cytokine induction. Our results demonstrate that stimulated T cells display bioactive lipids at their surface which induce cytokine production in human monocytes. The identification of these lipids might open the way to new therapeutic approaches in chronic/sterile inflammatory disorders such as rheumatoid arthritis and multiple sclerosis.