Evidence for suppressed activity of the transcription factor NFAT1 at its proximal binding element PO in the IL-4 promoter associated with enhanced IL-4 gene transcription in T cells of atopic patients

Allergen-specific T cells in atopic patients are polarized IL-4-produeing T (h)2 cells, promoting IgE synthesis by B cells, The molecular basis for inc reased IL-4 gene expression in atopy is not fully understood, IL-4 gene reg ulation in general involves the nuclear factor of activated T cells (NFAT) family of transcription factors, of which NFAT1 and NFAT2 are most prominen t in peripheral T cells, Recently, a unique inhibitory role of NFAT1 in IL- 4 gene control was shown in the mouse, In a series of electrophoretic mobil ity shift assays with protein extracts of highly polarized T(h)2 clones fro m atopics and T(h)1 clones from controls we compared DNA-binding activities at the two NFAT-binding elements P0 and P1 of the crucial proximal human I L-4 promoter, At the most proximal P0 site, NFAT-containing complexes devoi d of NFAT2 were readily inducible in the T(h)1 clones, but hardly or not in the T(h)2 clones. In contrast, both in T(h)1 and T(h)2 clones NFAT-contain ing complexes were strongly inducible at the P1 site, consisting of NFAT2 a nd a P0-competable NFAT activity, without apparent differences between T(h) 1 and T(h)2 clones, Like in T(h)2 clones, suppressed NFAT-P0 complex format ion was observed also at the polyclonal level in peripheral blood mononucle ar cells (PBMC) of three of five severe atopic dermatitis patients with str ongly elevated serum IgE levels, but not in control PBMC, These findings su ggest that high-lever IL-4 production in atopic T(h)2 cells is associated w ith selective reduction of suppressive NFAT1 activity at the IL-4 P0 elemen t and that some patients with this multifactorial disease may have a putati ve systemic disorder at this level.