Th-1 cytokines gene polymorphism in human brucellosis.

Brucellosis is a worldwide zoonosis. Infection with Brucella species results in the activation of cell-mediated immune response. The interaction between Th1and Th2 cytokines determines the outcome of disease. Production of each cytokine is in turn affected by genetic factors. In this study, we investigated the possible association between Th1 cytokines gene polymorphism and brucellosis. Different genotypes of TNF-alpha, IFN-gamma and IL-2 were determined by polymerase chain reaction-sequence-specific primer in 47 patients with brucellosis and in 166 healthy controls. Allele frequencies of these genotypes were compared using the chi2 test. The results showed a significant difference in the TNF-alpha genotype GG/GG in patients in comparison with controls (76.7% vs. 21%) (P = 0.001, OR = 12.42, 95%CI 5.7-27.7). There was no significant difference in the frequency distribution of the IFN-gamma genotypes between two groups. IL-2 GG genotype at position -330 was about two times more common in cases than in controls, but the difference was not significant (10.6 vs. 4.6 P value = 0.09). This study shows that genetically low producers of TNF-alpha are possibly susceptible to brucellosis and raise doubt about the role of gene polymorphism of INF-gamma in brucellosis which was demonstrated in previous studies. It seems that patients with brucellosis did not have a defect in producing IL-2 with even a trend towards producing higher amounts of this cytokine.