Prostaglandin synthesis in human T cells: its partial inhibition by lectins and anti-CD3 antibodies as a possible step in T cell activation.

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Abstract
The human leukemic T cell line Jurkat was used to study arachidonic acid (AA) metabolism. We demonstrated that Jurkat cells are able to convert AA into prostaglandins (PG) and thromboxanes. The presence of tritiated 6-keto-PGF1 alpha, PGE2, PGA2 (B2), and thromboxane B2 in the culture medium was shown either by thin-layer chromatography after a 4-hr incubation period of [3H]AA-prelabeled Jurkat cells or by using specific radioimmuno assays. PG synthesis was inhibited by both indomethacin and niflumic acid, two cyclooxygenase inhibitors. AA metabolism through the cyclooxygenase pathway was followed during T cell activation. T cells were activated by lectins or anti-CD3 monoclonal antibodies (mAb) to trigger the T3-Ti complex and by 12-0-tetradecanoylphorbol 13-acetate (TPA) to mimic IL 1-dependent pathways. Our results show that lectins and anti-CD3 mAb both reduce the amount of PG released by the cells, whereas TPA did not. We confirmed that a combination of TPA and lectins or TPA and anti-CD3 mAb is necessary to obtain full activation of Jurkat cells if this event is monitored by using measurement of IL 2 synthesis. In addition, lectins and anti-CD3 mAb can be replaced by the cyclooxygenase inhibitors indomethacin or niflumic acid. Indeed, a combination of TPA and one of these two drugs induced maximal IL 2 synthesis. These results thus suggest that a reduction in PG synthesis might be a prerequisite to allow the cascade of events involved in T cell activation.

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