Generation and Metabolism of Leukotrienes and Release of Histamine from Human Dispersed Tonsillar Cells

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Abstract
We studied the generation and metabolism of leukotrienes (LT) and the release of histamine by human tonsillar cell suspensions. Human tonsils were dissected and mechanically dispersed. This procedure yielded a single cell suspension with 1.6 .+-. 0.5 .times. 108 cells/g tissue consisting of 97.3 .+-. 0.4% lymphocytes, 1.4 .+-. 0.3% granulocytes, 1.3 .+-. 0.3% macrophages/monocytes, and 0.03 .+-. 0.02% mast cells/basophils. The cells were stimulated either with Ca-ionophore A23187, melittin, or anti-human IgE. Determination of the 5-lipoxygenase products LTB4 and LTC4 was performed with specific radioimmunoassays (RIA), and histamine release was measured by the fluorophotometric technique. A time- and dose-dependent release of the mediators was monitored. LTB, exceeded the amount of LTC4 in the supernatants. The concentration of leukotrienes ranged between 0.8 and 5.4 ng LTB4/1 .times. 108 cells or 0.5 and 1.5 ng LTC4/1 .times. 108 cells, depending on the stimulus. Histamine release after stimulation ranged between 25 and 35% of the total histamine content, whereas buffer controls amounted to 17%. The incubation of the cells (1 .times. 108) with exogenously added LTB4 resulted in the formation of .omega.-oxidated products (20-OH and 20-COOH-LTB4) and a novel unpolar metabolite, as identified by thin layer chromatography. This metabolite was not immunoreactive in the LTB4-RIA used. LTC4 and LTD4 were converted into LTE4 when added either to sonicated cells or to the cell-free supernatants of prestimulated tonsillar cells, indicating the release of .gamma.-glutamyltranspeptidase and dipeptidase, respectively. Our data clearly demonstrate the generation and metabolism of the 5-lipoxygenase products LTB4 and LTC4 as well as the release of histamine from human dispersed tonsillar cells, suggesting that they have a modulatory function with respect to the inflammatory potential at local sites.