Genetic factors seem to play a significant role in susceptibility to systemic lupus erythematosus (SLE). The purpose of this study was to investigate whether the amino acid polymorphism (Val14Met) found within the IFN-γ receptor gene (IFNGR1) plays a prominent role in susceptibility to SLE. We found Val14Met located at the COOH terminal of the signal peptide of the IFN-γ receptor. There was a significant difference in this polymorphism frequency between SLE patients and healthy populations. To clarify whether this amino acid substitution resulted in the alteration of the receptor function, we evaluated the induction of HLA-DR antigen expression on B cells by IFN-γ stimulation. There was also a significant difference in the induction of HLA-DR by IFN-γ stimulation between B cells. Furthermore, an intracellular cytokine assay indicated that the Th1/Th2 balance of Th cells bearing the variant receptor shifted to Th2. The genetic polymorphism found within the IFN-γ receptor gene (Val14Met) may result in a shift to Th2, and this shift may increase susceptibility to SLE.
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