The combination of rs2234711/rs1327474/rs7749390/rs41401746, which was in strong linkage disequilibrium (D′ > 0.75), showed a significant association of ifngr1 with tuberculosis (P = 0.00079). Neither the single SNP nor the haplotype analysis showed a significant association between tuberculosis and the ifng gene markers. Our data implied the involvement of the ifngr1 gene in susceptibility to tuberculosis. Tuberculosis has been declared a global emergency by the World Health Organization. In 2008, there were an estimated 8.9–9.9 million incident cases of tuberculosis and MLN0128 the 1.5–2.3 million deaths from

TB, mostly in developing countries [1]. Epidemiological data have revealed that only about one-tenth of the population that is infected by Mycobacterium tuberculosis will NVP-BEZ235 order develop clinical tuberculosis. Several twin studies have pointed

out significant differences in the development of tuberculosis between monozygotic and dizygotic twins [2], and there are significant racial differences in tuberculosis incidence. All these studies have indicated that genetic factors play an important role in the pathogenesis of tuberculosis [3]. Furthermore, the magnitude of the monozygotic to dizygotic difference has shown non-Mendelian inheritance, which implies that at least two and perhaps more interacting genes are involved [2]. Linkage-based, genome-wide screening of populations to determine the chromosomal location of genes involved in susceptibility to tuberculosis, as well as case–control association studies of candidate genes also have been carried out [4]. These results have indicated that polygenic factors contribute to the development of tuberculosis,

and ifng/ifngr1/ifngr2 stand out as some of main susceptibility genes for the disease [5, 6]. The Ribose-5-phosphate isomerase ifng gene is located on chromosome 12q24.1, and its protein product (interferon-γ; IFN-γ) is produced by lymphocytes activated by specific antigens or mitogens. IFN-γ shows antiviral activity and has important immunoregulatory functions. It is also a potent activator of macrophages and has antiproliferative effects on transformed cells. It can potentiate the antiviral and antitumor effects of the type I IFN [7]. A series of investigations has implicated ifng or IFN-γ in the pathological involvement of some infectious disorders, including hepatitis, AIDS and tuberculosis. Furthermore, the reeler mouse, a natural mutant that carries large deletions of the ifng gene, shows some alterations in its defence against M. tuberculosis [8]. These biochemical and in-vitro experimental data are supported by some association studies that have shown significant linkage between ifng gene polymorphism and tuberculosis.