Background The germline (GL) ɛ promoter is regulated by IL-4 and is essential for class switching to IgE. IL-4-induced gene expression is largely mediated through activation of latent transcription factor STAT6 (signal transducer and activator of transcription 6).
Objective We investigated whether increased levels of IgE in allergic individuals may be associated with alteration in the level or activation of STAT6 and subsequent increase in GL ɛ promoter activity.
Methods Electrophoretic mobility shift assay and Western blotting assays were used to investigate the level of expression and activation of STAT6 in Epstein–Barr virus (EBV)-transformed B cell lines from children with birch pollen allergy and their non-allergic siblings. The activity of the GL ɛ promoter was tested in a transient transfection assay.
Results STAT6 was expressed at the same level in all B cell lines tested. In two out of five sibling pairs STAT6 was activated by IL-4 more efficiently in the allergic individuals but in the three other pairs the opposite was found. In transient transfections, no difference in IL-4-induced GL ɛ promoter function was detected, although basal promoter activity varied between allergic and healthy siblings in two out of five pairs.
Conclusions We demonstrate for the first time that upon IL-4 signalling STAT6 transcription factor activation differs in B cells from different individuals. Although we did not find any association between STAT6 activation and allergy, we do not exclude a possibility that stronger activation of this transcription factor is associated with an expression of allergic phenotype.