Comparison of Genetic Polymorphisms of TNF-α and IL-10 Genes Between Tuberculosis Patients and Healthy Blood Donors

Background: Almost one-third of the world's population is infected with Mycobacterium tuberculosis, but only 10% of them develop tuberculosis. TNF-α/IL-10 balance has key roles in controlling latent/activation stages of tuberculosis. Objectives: The objective of this study was to determine an association between polymorphic variants of the TNF-α and IL-10 genes and tuberculosis. Patients and Methods: This case-control study was performed on 100 patients with tuberculosis (TB) and 194 healthy blood donors. There was no significant difference among the groups regarding gender and race (P > 0.05). The patients were diagnosed at Boo-Ali Hospital in Sistan-Baluchestan province, Iran. Polymerase chain reaction (PCR) was performed using commercially available CTS-PCR-SSP Tray Kit (University Clinic Heidelberg) for single nucleotide polymorphisms (SNPs) at IL-10 -1082 A/T, -819 C/T and -592 A/C; TNF-a-308 G/A and -238 G/A. Analysis of the specific amplicons was done by electrophoresis on 2% agarose gel containing 0.5 μg/mL ethidium bromide. Results were analyzed using the statistical software package SPSS 17.0 for Windows (SPSS Inc.). Results: A total number of 100 patients (50 with pulmonary TB [PTB] and 50 with extrapulmonary TB [EPTB]) and 194 healthy blood donors were genotyped. The results showed significantly increased frequency of AA genotype of IL-10 (C/A-592). Also, polymorphism was observed in EPTB patients compared to normal human subjects (NHS) and PTB patients (P = 0.05). The genotype frequency of IL-10 (C/T-819), IL-10 (G/A-1082) TNF-α (G/A-308) and TNF-α (G/A-238) did not show any significant difference. Frequency of high producing IL-10 (-819) T allele was significantly over-represented in EPTB group in comparison to both healthy blood donor and PTB groups (47.7% vs. 36.9%, P = 0.035; 47.7% vs. 31.8%, P = 0.03; respectively). Frequency of IL-10(-592) A allele was significantly increased in EPTB patients compared to NHS and PTB patients (51% vs. 37%, P = 0.01; 51% vs. 33%, P = 0.01; respectively). Conclusions: Results of the present study showed IL-10 gene polymorphism (C/T –819, C/A –592) plays a key role in susceptibility to or protection against EPTB development in the Iranian population.