Jurkat cells produced leukotriene C 4 and a small amount of leukotriene B 4 in response to CD3–CD28 cross-linking. Purified peripheral blood T lymphocytes were incapable of synthesizing leukotrienes in the absence of exogenous arachidonic acid. Fluorescence-activated cell sorter analysis of different T-lymphocyte populations, including CD4, CD8, CD45RO, CD45RA, T helper type 2, and T-cell receptor-αβ and -γδ expressing cells, did not identify a differential distribution of the enzyme. 5-LOX was present primarily in the cytoplasm with some nuclear localization and was translocated to the nuclear periphery after culture in a mitosis-supporting medium. 5-LOX protein expression was confirmed by Western blot and immunofluorescence studies. Messenger RNA (mRNA) of 5-LOX was amplified by conventional reverse transcription–polymerase chain reaction (RT-PCR MOLT4 and Jurkat cells) and by in situ RT-PCR (T lymphocytes). In this study, we provide evidence for 5-LOX expression on both transcriptional and translational levels in highly purified peripheral blood T cells as well as in human T lymphoblastoid cell lines (MOLT4 and Jurkat). Its presence has been reported in cells of the myeloid lineage and B lymphocytes but has not been formally defined in T lymphocytes. 5-lipoxygenase (5-LOX) is the key enzyme responsible for the synthesis of the biologically active leukotrienes.
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