In stage I of 48 cases and 48 controls, the rs2227473 marker, which is located in -1756 bp upstream of the IL-22 gene transcription start site (TSS), was in Hardy-Weinberg equilibrium. The minor allele frequency of 0.103 in the control is comparable to the annotations in the HapMap (0.102 for CHB+JPT, 0.120 for YRI, and 0.208 for CEU). The ‘A' allele is associated with decreased risk of TB susceptibility at p-value of 0.0275, with odds ratio (OR) of 0.188 (confidence interval (CI) = 0.037–0.967), as shown in Table 1. The haplotype analysis was further performed in the surrounding region of this SNP. We found that the haplotype TCATGA—which is made of SNPs rs2227485, rs2227484, rs2227483, rs2227478, rs2227473, and rs2227472—shows a trend of association with decreased risk of TB susceptibility at p-value of 4.89E-5 (Supplementary Table S1). We therefore selected these 6 SNPs for genotyping in the second stage.