Arachidonic acid can be metabolized to form a group of compounds known as the cysteinyl leukotrienes (CysLT) that bind to one of two receptors to mediate their actions. On circulating cells, expression of the leukotriene receptors is low, but in inflamed tissue the receptor number is dramatically increased. We hypothesized that the cytokine milieu present during inflammation can increase receptor expression on infiltrating immune cells. Various cell populations were purified from peripheral blood and stimulated in vitro with cytokines characteristic of allergic inflammatory disorders, and CysLT receptor expression was measured using quantitative PCR analysis, Western blot, and flow cytometry. IL-4, but not IL-13, was able to significantly induce mRNA and protein levels for both CysLT receptor 1 and 2 from T cells and B cells. CysLT2 receptor expression was also significantly increased in monocytes and eosinophils after IL-4 stimulation. Surprisingly, CysLT2 receptor expression was increased in monocytes, T cells, and B cells when IFN-␥ was used as the stimulus. Factors involved in eosinophil growth and survival were tested for their ability to alter CysLT receptor expression. These results support the concept that cytokines increase expression of both receptors on lymphocytes and granulocytes, allowing these cells to be more responsive to secreted leukotrienes at sites of inflammation.Keywords: cysteinyl leukotriene receptor; T cell; B cell; eosinophil; cytokine In 1937, the slow-reacting substance of anaphylaxis was described based on the identification of a mediator derived from activated mast cells that, in an antihistamine-resistant fashion, mediated the sustained, prolonged contraction of smooth muscle. This mediator was later identified as a group of compounds known as the cysteinyl leukotrienes (CysLTs). Leukotrienes (LTs) are derived from the metabolism of arachidonic acid. Membrane phospholipids are converted into arachidonic acid by the action of a family of enzymes termed phospholipase A 2 . With cell activation, the enzyme 5-lipoxygenase (5-LO) translocates from the cytosol to the inner nuclear membrane, where in association with 5-lipoxygenase-activating protein (FLAP), it oxygenates and then dehydrates arachidonic acid to generate LTA 4 (1). LTA 4 can be conjugated with the tripeptide glutathione into the cysteinyl leukotriene LTC 4 by the enzyme LTC 4 synthase (LTC 4 S) (or the related enzyme microsomal glutathione (Received in original form July 12, 2006 and in final form January 29, 2007 ) This study was supported by a medical school grant from Merck and Co., PO1 AI50989, AI057438, and AI47737.Correspondence and requests for reprints should be addressed to John W. Steinke, Asthma and Allergic Disease Center, Box 801355, University of Virginia Health System, Charlottesville, VA 22908. E-mail: js3ch@virginia.edu This article has an online supplement, which is accessible from this issue's table of contents at www.atsjournals.org. CLINICAL RELEVANCEThese results show that the inflammatory milieu...

Transcriptional dysregulation of the IL-10 gene may contribute to the development and severity of autoimmune, infectious, neoplastic, and allergic diseases. A C to A base substitution has been identified at −571 bp in the IL-10 promoter and has been linked to immune diseases. The role of this polymorphism in IL-10 promoter function was assessed using luciferase reporter constructs. The presence of an A at −571 (A allele) increases promoter activity compared with that of a promoter with a C at this position (C allele). Binding of nuclear extract proteins from IL-10-producing human cell lines to DNA sequences including this base exchange and flanking sequences was demonstrated using EMSAs. Specific binding of the transcription factors Sp1 and Sp3 was demonstrated to a region immediately upstream of the polymorphism. No differences in the binding affinity of recombinant Sp1 were observed between the two forms of the promoter. Reconstitution of Sp1 expression decreased IL-10 promoter function in an Sp1-deficient cell line, demonstrating that this element functions as a repressor. The C to A base exchange relieves the repression mediated by Sp1. Individuals carrying the A allele of the IL-10 promoter may display increased synthesis of IL-10, resulting in suppressed immune responses and a modulation of their susceptibility to autoimmune, infectious, neoplastic, or atopic disease.

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