Association of TBX21 promoter polymorphisms with type 1 autoimmune hepatitis in a Chinese population

The T-box transcription factor T-bet is a key regulator for the lineage commitment in CD4 Th1 cells and CD8 T cells by activating the hallmark production of interferon-γ, and its expression level is linked to autoimmune diseases. T-1993C and T-1514C polymorphisms in the TBX21 gene (encoding T-bet) promoter can affect transcription activity. We investigated the distributions of these functional polymorphisms in 84 adult patients with type 1 autoimmune hepatitis (AIH-1) and 318 healthy controls. Intracellular T-bet staining of polarized CD4 Th1 cells from healthy controls corresponding to T-1993C genotypes were analyzed by flow cytometry. The -1993C allele frequency was 3.0% in AIH-1 and 11.8% in controls (p = 0.000 25). Individuals carrying the -1993C allele had a decreased risk to AIH-1 compared with those without the -1993C allele (p = 0.0016, odds ratio [OR] = 0.22, 95% confidence interval = 0.09-0.56). No association was found between the T-1514C polymorphism and AIH-1. The onset age of AIH-1 was also accelerated among -1993TT homozygotic individuals (p = 0.013). The fractions of T-bet positive Th1 cells in the -1993TT homozygotes were 2.2-fold higher than those in -1993CC homozygotes (p = 0.002). Our results suggest that the T-1993C polymorphism in the TBX21 promoter influences susceptibility to AIH-1 in a Chinese population.