Objectives: This study investigated and analyzed the association of interferon-γ (IFN-γ) gene polymorphisms and Th1/Th2 balance in tuberculosis susceptibility.
Methods: From January 2018 to January 2020, 121 tuberculosis patients that were hospitalized for initial treatment and were chosen as the pulmonary tuberculosis group, and another 80 healthy individuals with physical examination in the same period were selected as the control group. The genetic distribution of IFN-γ +874 sites in the two sets of subjects was detected by sequence-specific primer PCR (PCR-SSP), the serum IFN-γ level was detected by ELISA, and the ratio of Th1 and Th2 on cells in two sets of subjects were detected by flow cytometry. Subsequently, we compared the differences in IFN-γ degree and the changes in Th1/Th2 in patients with different genotypes.
Results: The difference in the distribution of IFN-γ (+874 T/A) genotype frequencies between the two groups of subjects was significantly different (P<0.05), and the frequency of A allele in the tuberculosis group was clearly higher than that in the control group (P<0.05). Compared with the control group, the Th1 cells percentage in the pulmonary tuberculosis group decreased remarkably, the Th2 cells percentage increased significantly, while the Th1/Th2 ratio was notably decreased (P<0.05). In addition, the Th1/Th2 ratio in tuberculosis patients with an IFN-γ (+874 T/A) genotype AA was remarkably lower than those with AT+TT genotype (P<0.05).
Conclusion: An AA genotype with IFN-γ (+874 T/A) is a susceptible genotype for tuberculosis. The mechanism may be related to the imbalance of Th1/Th2 which is more likely to occur in patients with AA genotype. This can lead to a decline in immune function of the body, making it more susceptible to infection with mycobacterium which induces tuberculosis.
Keywords: Polymorphism of IFN-γ gene; Th1/Th2 balance; susceptibility; tuberculosis.
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