This polymorphism is referenced as a deletion/insertion polymorphism with the RefSNP rs34820341 in NCBI. Here, we termed the two alleles containing one or two repeats,*V1 and *V2, respectively. The *V1 allele corresponds to the reference sequence of IDO1 available in the GenBank database with the accession number NT_007995 and the sequence of the *V2 allele has been deposited in GenBank under the accession number JN382541. No other mutation was identified in the 1.6-kb promoter region of the 41 sequenced DNA samples. The genotype and allele frequencies of the VNTR polymorphism in the 41 Caucasian volunteers, that were calculated based on the sequencing approach, are shown in Table 2. Using a rapid PCRbased genotyping assay, statistically similar genotype and allele frequencies were GDC-0199 observed with the 300 DNA samples from the Haguenau cohort . The frequency of the *V1 and *V2 alleles is around 46�C48% and 52�C54%, respectively, and the distribution of the VNTR genotypes respects the Hardy-Weinberg law. A gene reporter assay was developed in order to assess the impact of the VNTR on the transcriptional activity of the IDO1 promoter. The luciferase activities shown in Figure 2A were measured under basal conditions or after stimulation by IFN-c and/or TNF-a. Under basal conditions, the relative luciferase activities of the *V1 and *V2 alleles were increased 2.5-fold compared to the insertless promoter, which confirms that the 1.6-kb promoter region of IDO1 has significant transcriptional activity. The transcriptional activity of the IDO1 promoter was also evaluated after 24 h stimulation with IFN-c and/or TNF-a, two cytokines that are known to induce IDO1 expression. Stimulation by IFN-c and TNF-a separately showed a respective 105- and 10-fold increase in luciferase activity of the *V1 and *V2 alleles compared to the pGL4 insertless vector . Stimulation in the presence of both IFN-c and TNF-a resulted in a 250- and 277-fold increase in *V1 and *V2 luciferase activity, respectively . These data confirm the induction of IDO1 expression via a transcriptional mechanism Y-27632 through cytokines stimulation.