Detection of IL-9 producing T cells in the PBMCs of allergic asthmatic patients

Background: Interleukin-9 (IL-9) was reported as an active participant in the pathogenesis of allergic asthma. This study aimed to investigate the major source of IL-9 and its effect on interferon. (IFN-gamma) and immunoglobulin (Ig) secretion by B cells. Methods: We isolated peripheral blood mononuclear cells from children with allergic asthma and healthy children. IL-9, IL-4 and IFN-gamma expression were detected by ELISA, ELISpot and Flowcytometry. Expression of transcription factor PU. 1 was measured by Western Blot. We evaluated the effect of IL-9 on B cell activation and Ig production. Results: Results showed that compared with healthy children, levels of IL-9, IL-4 and PU. 1 were elevated and levels of IFN-. were lower in children with allergic asthma. IL-9-expressing CD4(+) T cells did not co-express IL-4. Exogenous IL-9 inhibited IFN-gamma production in a dose-dependent manner. Antigen-specific Th9 cells existed in children with house dust mite allergic asthma. IL-9 up-regulated expression of CD69 and CD25 on B cells and combination of IL-9 and IL-4 enhanced IgE production. Conclusions: In conclusion, our results showed that Th9 cells may be the major source of IL-9 in children with allergic asthma. In these patients, IL-9 impairs IFN-gamma production and synergistically promotes IL-4-induced IgE secretion.