A CTLA-4 gene polymorphism at position -318 in the promoter region affects the expression of protein.

CTLA-4 is an important negative regulator of the immune system. The regulation of the CTLA-4 gene (Ctla-4) transcription is poorly understood. A single nucleotide polymorphism (SNP) at -318 in the Ctla-4 promoter region is associated with certain autoimmune diseases. Since the -318 SNP occurs in a potential regulatory region, it is conceivable that the C' T transition may affect the expression of Ctla-4. In the present study, we show that the -318T allele is associated with a higher promoter activity than the -318C allele (8.13 +/- 0.46 vs 6.87 +/- 0.49). The presence of the -318T allele may thus contribute to up regulation of the expression of CTLA-4, and consequently represent one mechanism to inhibit exaggerated immune activity.