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-α, IFN-γ 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 χ2 test. The results showed a significant
difference in the TNF-α 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-γ 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-α are possibly susceptible to brucellosis
and raise doubt about the role of gene polymorphism of
INF-γ 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
