T‐bet is a key regulator for the lineage commitment in CD4 T helper (Th) 1 cells by activating the hallmark production of interferon‐γ, and its expression level is linked to autoimmune, infectious, and allergic diseases. A T to C base substitution has been identified at position ‐1993 in the TBX21 (encoding T‐bet) promoter and has been associated with asthma and systemic lupus erythematosus. This study aimed to investigate the molecular mechanisms responsible for the influence of the T‐1993C polymorphism on transcription and its functional effect by luciferase reporter, EMSAs, Chromatin immunoprecipitation assay, and flow cytometric analysis of intracellular T‐bet, IFN‐γ and IL‐4 expression in activated CD4+ T cells. The presence of a ‐1993T allele obviously increases promoter activity compared with that of a promoter with a ‐1993C allele. TBX21 promoter carrying ‐1993C allele possesses significantly stronger binding affinity to the Yin Yang 1 (YY1) transcription factor than that carrying ‐1993T allele. YY1 overexpression decreased TBX21 promoter function in a T cell line, demonstrating that this element functions as a repressor. The C to T base exchange relieves the repression mediated by YY1. The individuals carrying ‐1993C allele were determined to have significantly diminished expression of TBX21 and IFN‐γ and increased IL‐4 production in cells compared with the individuals carrying ‐1993T allele (P < 0.05). These findings demonstrate that the TBX21 T‐1993C polymorphism represses TBX21 expression and Th1 cytokine production through control of YY1, which might result in the imbalance between Th1 and Th2 immune responses in autoimmune or allergic diseases.

Aims:  The aim of this study was to classify Edwardsiella strains isolated from China aquaculture based on biochemical and molecular methods. Methods and Results:  In this study, biochemical characterization of 19 Edwardsiella tarda isolates and two Edwardsiella ictaluri isolates was performed with API 20E system. Other pathogenicity‐related phenotypes such as haemagglutination, haemolytic activities and lethality to fish were also examined in these strains. As it was difficult to categorize the subgroups of Edw. tarda according to their origins or phenotypic properties, three PCR‐based methods, i.e. PCR amplification of virulence genes, Enterobacterial repetitive intergenic consensus‐PCR and BOX‐PCR, were carried out to further resolve the relatedness of the Edw. tarda isolates. As a result, all Edw. tarda isolates could be generally grouped into pathogenic and nonpathogenic branches before being classified into strain‐specific or origin‐specific clades. Conclusions:  Biochemical characterization was sensitive for interspecific typing, while PCR‐based approaches permitted a more accurate discrimination for intraspecific typing resulting in pathogenic and nonpathogenic clusters and further more delicate clades for Edwardsiella. Significance and Impact of the Study:  PCR‐based genomic fingerprinting to study the relatedness and trace the pathogenicity of the Edwardsiella strains will be helpful in investigating the virulence factors of Edwardsiella and in the development of vaccines and diagnostics for edwardsiellosis.