Leukotriene B4 induces interleukin 5 generation from human T lymphocytes

Abstract
Leukotriene B4 (LTB4) has been shown to affect several interleukin (IL)‐linked functions of human lymphocytes. In this study, we investigated whether LTB4 regulates IL‐5 generation from human T cells and subsequently modulates eosinophil functions. Preincubation of T cells with very low concentrations (10−12 to 10−8M) of LTB4 induced concentration‐dependent IL‐5 production, the event occurring after the first 24 h of cultivation. However, direct action of LTB4 to IL‐5 generation is strictly dependent on a preincubation with appropriate concentration of LTB4. In contrast, the stereoisomer of LTB4,5S,12S‐dihydroxy‐6,8,10,14‐eicosatetraenoic acid showed no enhancement of IL‐5 production. IL‐5 released from LTB4‐primed T cells elicited sustained viability of mature eosinophils and reduced the content of eosinophil cationic protein in their crystalloid matrix by degranulation. These data suggest that LTB4 induces bioactive IL‐5 production from T cells and that the released IL‐5 modulates eosinophil functions which might play a crucial role in eosinophil‐linked allergic inflammatory process.