We found a novel polymorphism, −66T/C, in the promoter region of human FcεRIα, the specific component of the high affinity receptor for IgE (FcεRI), which is essential for the cell surface expression of FcεRI and the binding of IgE Ab. When the effect of the single nucleotide replacement on the promoter function was analyzed, the transcription activity of the T allele promoter was found to be higher than that of the C allele promoter, and was markedly up-regulated by the overexpression of GATA-1 when compared with the C allele promoter. This is probably because the promoter with T at −66 has an additional GATA-1-binding motif in the region, which may assure higher affinity of the transcription factor to the promoter. In accordance with this, EMSA actually indicated that GATA-1 bound to the T allele probe (−80/−59) with the affinity higher than that to the C allele probe. Statistical analysis suggested that a significant portion of nonallergic individuals has heterozygous −66T/C genotype, while most of allergic individuals have homozygous −66T/T genotype in Japanese population. Our findings for the first time demonstrate the presence of FcεRIα polymorphism related to the allergic diseases.

Transcriptional regulation of the gene-encoding human FcεRI α-chain was analyzed in detail. EMSA revealed that either YY1 or PU.1 bound to the region close to that recognized by Elf-1. The α-chain promoter activity was up-regulated ∼2-fold by exogenously expressed YY1 or PU.1 and ∼7-fold by GATA-1, respectively, in KU812 cells. In contrast, coexpression of GATA-1 with either of PU.1 or YY1 dramatically activated the promoter ∼41- or ∼27-fold, respectively. Especially synergic activation by GATA-1 and PU.1 was surprising, because these transcription factors are known to inhibit the respective transactivating activities of each other. These up-regulating effects of PU.1 and YY1 with GATA-1 were inhibited by overexpression of Elf-1, indicating that Elf-1 serves as a repressor for the α-chain gene expression. Transcriptional regulation of the α-chain gene through four transcriptional factors is discussed.

The β subunit of the high-affinity IgE receptor (FcεRI) plays an important role in IgE-mediated allergic reactions as an amplifier for cell surface expression and signal transduction of FcεRI. FcεRIβ is presumed to be one of the genes linked with atopic diseases. However, the validity of the associations previously found between single nucleotide polymorphisms (SNPs) in FcεRIβ and atopic diseases is questionable. In the present study, we found correlation between the SNP of FcεRIβ at +6960A/G, resulting in a Glu237Gly amino acid substitution, and the cell surface expression level of FcεRI on blood basophils, although it has been shown that the Glu237Gly mutation itself does not affect the surface expression or function of FcεRI. We additionally found four SNPs in the promoter region of FcεRIβ, among which −426T/C and −654C/T were tightly linked with +6960A/G. Reporter plasmids carrying the −426C and −654T promoter displayed higher transcriptional activity than those carrying the −426T and −654C promoter. We found that transcription factor YY1 preferentially bound and transactivated the −654T promoter. Furthermore, expression of FcεRI β-chain mRNA in basophils from individuals who have the minor heterozygous genotype was significantly higher than that of the major homozygous genotype. These results suggest that the SNPs in the FcεRIβ promoter are causally linked with atopy via regulation of FcεRI expression.

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High-dose intravenous immunoglobulin (IVIG) therapy is well established as a standard therapy for Kawasaki disease (KD) that reduces the risk of developing coronary artery aneurysms. Activation of monocytes/macrophages and tumor necrosis factor-alpha (TNF-alpha) activity are responsible for severe vascular injury in acute KD. We examined whether or not IVIG inhibits TNF-alpha-induced activation of transcription factor NF-kappaB, a factor that is essential for the expression of proinflammatory cytokines, in human monocytic U-937 cells. The inhibitory effect of IVIG on NF-kappaB activation induced by TNF-alpha was evaluated by Western blotting and flow cytometry. In addition, we examined the effect of IVIG on the expression of FcgammaIII (CD16) and FcgammaRIIb (CD32b) in U-937 cells and peripheral blood CD14+ monocytes/macrophages by flow cytometry. Western blotting demonstrated that IVIG inhibits NF-kappaB activation in U-937 cells, and flow cytometry that IVIG inhibits NF-kappaB activation in U-937 cells in a dose-related manner. Western blotting of cytoplasmic extracts of U-937 cells revealed that IVIG inhibited degradation of the IkappaBalpha protein. Moreover, flow cytometry demonstrated that IVIG decreased the expression of FcgammaRIII in U-937 cells and peripheral blood CD14+ monocytes/macrophages. However, Western blotting revealed that IVIG did not affect the quantity of FcgammaRIII protein, and PCR that IVIG did not affect the quantity of FcgammaRIII mRNA in the cells. These findings suggest that IVIG inhibits TNF-alpha-induced NF-kappaB activation in monocytes/macrophages, and blocks FcgammaRIII on the membranes of monocytes/macrophages.