T-cell immunoglobulin- and mucin-domain-containing molecule 3 gene polymorphisms and renal cell carcinoma

T-cell immunoglobulin- and mucin-domain-containing molecule 3 (TIM-3) is a novel transmembrane protein that is involved in the regulation of T-helper 1 (Th1)-cell-mediated immunity. This study was undertaken to investigate the association of TIM-3 polymorphisms with susceptibility to renal cell carcinoma (RCC) in the Chinese population. Blood was collected from 322 RCC patients and 402 healthy controls. Three polymorphisms in the TIM-3 gene (-1516G/T, -574G/T, and +4259T/G) were genotyped by polymerase chain reaction-restriction fragment length polymorphism. Results showed that the -574G/T and +4259T/G polymorphisms were significantly increased in the RCC cases (odds ratio [OR] = 2.77, 95% confidence interval [CI], 1.42-5.39, p = 0.002 and OR = 3.22, 95% CI, 1.64-6.35, p<0.001). When analyzing the haplotypes of TIM-3 polymorphisms, TTG (-1516, -574, and +4259) revealed a significant correlation with RCC (OR = 3.55, 95% CI, 1.13-11.2, p = 0.033). In addition, the prevalence of +4259T/G polymorphism was higher in RCC cases with metastasis than in those without metastasis (7.4% vs. 3.5%, p = 0.041). These results suggest that polymorphisms in the TIM-3 gene are new risk factors for RCC and that TIM-3 may play important roles in regulating the prognosis of this disease.     

Expression of T-cell immunoglobulin- and mucin-domain-containing molecules-1 and -3 (Tim-1 and Tim-3) in Helicobacter pylori infection

Background: Th immune response plays an important role in Helicobacter pylori (H. pylori) infection. Tim‐1 and Tim‐3 are expressed on terminally differentiated Th2 and Th1 cells, respectively, and participate in the regulation of Th immune response. Until now, the role of Tim in H. pylori infection remains unclear. Materials and Methods: (1) Lymphocytes isolated from the spleen of BALB/c mice were co‐cultured with different concentrations of viable H. pylori. Alternatively, mice were challenged by viable H. pylori to set up the H. pylori infection model. (2) The expression of Tim‐1 and Tim‐3 on mRNA level in lymphocytes or spleen of mice was determined by RT‐PCR. The percentage of Tim‐3‐positive cells was determined by flow cytometric analysis. The production of cytokine in supernatants was measured by standard sandwich cytokine ELISA. Results: (1) Co‐culture: At 12 hours, there was markedly decreased production of Tim‐1 and increased production of Tim‐3 in lymphocytes co‐cultured with H. pylori compared with normal control. The change of Th2 cytokine had the similar tendency as that of Tim‐1 expression; alternatively, the change of Th1 cytokine had the similar tendency as that of Tim‐3 expression. (2) Infection: Tim‐1 expression was declined in infected mice compared with control group; in the contrast, Tim‐3 expression was increased. Furthermore, the expression of Tim‐1 and Tim‐3 mRNA in spleen was significantly positively correlated with the level of Th2 and Th1 cytokine in gastric homogenized supernatant, respectively. Conclusion: H. pylori could inhibit the differentiation of T lymphocytes toward Th2 cells, promote the Th1 cell differentiation, and induce Th1‐biased immune response. The expression of Tim‐1 and Tim‐3 could reflect Th2 and Th1 immune response, respectively, which provide evidence for the prevention and treatment of H. pylori infection and correlation diseases through regulation of Tim‐1 and Tim‐3.     

Investigation of the VDR gene polymorphisms association with susceptibility to colorectal cancer

The effects of 1,25-dihydroxyvitamin D3 are mediated by binding to a specific intracellular vitamin D receptor (VDR), which has been identified in a variety of tissues. Certain polymorphisms in the VDR gene have been associated with various neoplasms. For this purpose, we studied whether VDR TaqI or FokI genotype are associated with serum 25-hydroxyvitamin D3 in 52 controls and 26 patients with colorectal cancer. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP), and agarose gel electrophoresis tecniques were used to detect these polymorphisms. We measured 25-hydroxyvitamin D3 serum levels by ELISA. The frequencies of the FF, Ff and ff genotypes were 73.1%, 11.5%, 15.4% in colorectal cancer patients and 38.5%, 59.6%, 1.9% in healthy controls, respectively. We observed the T allele in 50% and 58.7%, and the t allele in 50% and 41.3% of colorectal cancer patients and the control group, respectively. In patients with colorectal cancer who have TT genotype, serum 25-hydroxyvitamin D3 level was lower than those with Tt/tt genotype (p:0.016). The frequency of subjects with TTFf or TtFf genotype in colorectal cancer patients was very low compared with all other genotypes (OR = 0.112; 95%CI 0.030-0.419). These data suggest that VDR TtFf or TTFf genotypes may protect against colorectal carcinogenesis. However, further studies are necessary to confirm these findings.     

The association between N-acetyltransferase 2 gene polymorphisms and pancreatic cancer

Pancreatic cancer has been linked with exposure to environmental chemicals, which generally require metabolic activation to highly reactive toxic or carcinogenic intermediates. N-acetyltransferase 1 (NAT1) and N-acetyltransferase 2 (NAT2) are expressed primarily in extrahepatic and hepatic tissues, respectively. Both enzymes catalyze N- and O-acetylation of aromatic and heterocyclic amines. It is believed that these compounds are activated via O-acetylation and detoxified by N-acetylation. Several polymorphisms of these two genes have been associated with an increased risk of cancer. Twenty-seven cases of pancreatic cancer and 104 controls were included in this study. Blood was collected in EDTA-containing tubes, and genomic DNA was extracted from the white blood cells by using a high pure PCR template preparation kit. Genotyping of NAT2 polymorphisms was detected by a real time PCR instrument. There was a significant difference in the distribution of the NAT2*6A acetylators phenotype between cases and the controls. The odds ratio of pancreatic cancer for the NAT2*6A slow phenotype was 5.7 (95% CI = 1.27-25.55; p = 0.023) compared with the fast type. Our results suggest that slow acetylators have higher risk of developing pancreatic cancer than fast acetylators. NAT2 gene polymorphisms may be associated with genetic susceptibility to pancreatic cancer.     

IL6 gene polymorphisms and susceptibility to colorectal cancer: a meta-analysis and review

A number of case-control studies were conducted to investigate the association of IL6 gene polymorphisms with colorectal cancer (CRC). However, the results were not always consistent. We performed a systematic review and meta-analysis to examine the association between the IL6 gene polymorphisms and CRC. Data were collected from the following electronic databases: PubMed, EMBASE, Web of Science, BIOSIS Previews, HuGENet, and Chinese Biomedical Literature Database, with the last report up to July 2011. A total of 17 studies involving 4 SNPs were included (16 for rs1800795, 2 for rs1800796, 2 for rs1800797, and 1 for rs13306435). Overall, no significant association of these polymorphisms with CRC was found in heterozygote comparisons as well as homozygote comparison, dominant genetic model and recessive model. In subgroup analysis, among studies using population-based controls, fulfilling Hardy-Weinberg equilibrium, or using Taqman genotyping method, we did not find any significant association. However, the rs1800795 C allele was significantly associated with reduced risk for CRC among persons who regularly or currently took NSAIDs (four studies, OR = 0.750; 95 % CI, 0.64-0.88; P = 0.474 for heterogeneity test), and with increased risk for CRC among persons who drank (one study, OR = 1.97; 95 % CI, 1.32-2.94). Individuals with the rs1800795 C allele in the IL6 gene have a significantly lower risk of CRC, but in the setting of NSAIDs use. Further studies are merited to assess the association between the IL6 gene polymorphisms and CRC risk among persons who take NSAIDs, drink or smoke, etc.     

Impact of MMP-3 and TIMP-3 gene polymorphisms on prostate cancer susceptibility in North Indian cohort

Purpose

Matrix metalloproteinases (MMPs) have been implicated in progression and metastases of different tumors. The balance between the MMPs and their natural inhibitors (tissue inhibitors of matrix metalloproteinases; TIMP) seem to be an important factor related to its role. The purpose of this study was to evaluate polymorphisms in the MMP-3 and TIMP-3 genes for their associations with prostate cancer (PCa) risk in North Indians.

Materials and methods

Genotypes were determined by PCR-RFLP (Polymerase Chain Reaction Restriction Fragment Length Polymorphism) method in 150 PCa patients and 200 age matched controls of similar ethnicity.

Results

We found significant association in the MMP-3(1171)5A/6A and TIMP-3 (1298) C/T polymorphism with PCa risk. Variant genotype (5A/5A) of MMP-3(1171)5A/6A polymorphism had a high PCa risk (p = 0.037, OR = 3.52, 95%CI = 1.08–11.5). Individuals with TIMP-3 (1298) CT genotype as well as T allele showed reduced risk of PCa (p < 0.001; OR = 0.31; 95%CI = 0.18–0.52, and p = 0.001; OR = 0.49; 95%CI = 0.32–0.75). This effect was even more evident in case of T allele carrier (CT + TT) (p < 0.001; OR = 0.36; 95%CI = 0.22–0.59). Overall no significant association was observed statistically in MMP-3 and TIMP-3 with any of the grading stages and smoking habits in PCa. Haplotype analysis of MMP-3 showed that A-5A-A was associated with three folds (OR = 3.06; 95%CI = 1.71–5.47; p < 0.001) increased risk in PCa patients.

Conclusion

This is the first reported association between polymorphisms in the MMP-3 and TIMP-3 gene and PCa risk and supports the hypothesis that the protease/antiprotease balance has an important role. Due to the small sample size further investigations need to be done to prove a statistical significant correlation between the MMP/TIMP expression and clinicopathological parameters.     

T cell costimulatory molecule function determines susceptibility to infection with Pneumocystis carinii in mice

Loss of T cell number and function during HIV infection or secondary to pharmacologic immunosuppression renders individuals susceptible to opportunistic infections, including Pneumocystis carinii pneumonia. Because costimulatory receptors are critical for optimal T cell function, we hypothesized that these proteins would regulate susceptibility to opportunistic infections. We found that despite normal T cell numbers, mice deficient in the costimulatory molecules CD2 and CD28 spontaneously developed P. carinii pneumonia. In experiments using intratracheal injection of P. carinii organisms to induce infection, the loss of CD28 alone was sufficient to render mice susceptible to acute infection; however, the organism was eventually cleared. Examination of inflammatory responses to P. carinii revealed that mice deficient in both CD2 and CD28 accumulated CD8(+) T cells in their lungs in response to infection and demonstrated markedly reduced specific Ab titers. Analysis of cytokine profiles suggested that regulation of IL-10 and IL-15 may be important elements of the response to this pathogen. Thus, costimulatory molecule function is critical in determining the initial susceptibility to infection with P. carinii. Analysis of immunologic responses in these mice may provide important insights into the defects that render individuals susceptible to opportunistic infection, and provide opportunities for novel immunologically based therapies.     

Association of genetic polymorphisms in vitamin D receptor gene and susceptibility to sporadic prostate cancer

Genetic and environmental factors are involved in prostate cancer (PCa) etiology. Single nucleotide polymorphisms (SNPs) may contribute to the PCa pathogenesis. The goal of this study is to determine the role of vitamin D receptor (VDR) gene polymorphisms and haplotypes in the development and progression of sporadic PCa. One hundred and thirty-three PCa patients and 157 age-matched healthy controls were genotyped for the Apa I (rs7975232), Bsm I (rs1544410) and Taq I (rs731236) polymorphisms in VDR gene by using polymerase chain reaction-restriction fragment length polymorphism. An association was observed between the Apa I polymorphism and PCa predisposition (P = 0.03). When compared with AA genotype, there was a highly notable difference in the frequencies of the Aa (P = 0.02), aa (P = 0.026) and Apa I 'a' allele carriers (Aa + aa) (P = 0.009) genotypes. Furthermore, we found a statistical difference in the allele frequencies of the Apa I polymorphism between the sporadic PCa patients and control subjects (P = 0.013). The genotype distribution for the Bsm I and Taq I polymorphisms were similar between cases and controls (P > 0.05). No clinically significant relationship was found between the three-locus haplotypes and development of sporadic PCa. The genotype frequencies for the three polymorphisms of the VDR gene within subgroups of PCa (defined by tumor stage, Gleason score, PSA levels) were also analyzed, but no statistically noteworthy difference was observed (P > 0.05). As far as we know, this is the first study which investigates the relationship between VDR genotypes and sporadic PCa in the Turkish population. Our findings suggest that the VDR ApaI (rs7975232) polymorphism may play a role in the development of sporadic PCa.     

细胞色素P4501B1基因多态性与乳腺癌易感性研究进展

细胞色素P450（cytochrome,CYP）1B1是P450超基因家族酶系的一个重要成员,广泛分布于肝外组织,其代谢受到外源性致癌物、雌激素等多种因素的调控。该基因存在遗传多态性,艮前已对CYP1B1基因多态性与乳腺癌易感性进行了多项研究。本文就CYP1B1基因的多态性、调控机制及其与乳腺癌的关系进行了综述。     

Genetic polymorphisms of XRCC1 gene and susceptibility to gastric cancer in Chinese Han population

Abstract

This study aims to evaluate whether the c.1471G?>?A and c.1686C?>?G genetic polymorphisms of XRCC1 gene influencing gastric cancer susceptibility. A total of 813 subjects with Chinese Han ethnicity were enrolled. Our data suggest that the allele and genotype frequencies are significantly different from gastric cancer patients with cancer-free controls. We find that c.1471G?>?A and c.1686C?>?G genetic polymorphisms statistically increase the risk of gastric cancer. Our findings indicate these two genetic polymorphisms are related with the susceptibility to gastric cancer, and could be used as molecular markers for detecting gastric cancer in Chinese Han ethnicity.     

Promoter polymorphisms in DNA repair gene ERCC5 and susceptibility to gastric cancer in Chinese

Genetic variations in excision repair cross-complementing group 5 (ERCC5) might influence individual vulnerability to gastric cancer (GC). We investigated effects of two putatively functional polymorphisms in ERCC5 promoter region, rs751402 (+ 25A > G) and rs2296147 (+ 202C > T), and their potential interaction with environment factors on the risk of developing GC. We performed a sex- and age-matched case–control design with 400 GC cases and 400 healthy controls for rs751402 and 403 GC cases and 403 healthy controls for rs2296147. Our results showed that rs751402 were associated with increased GC risk (AA vs. GG: OR = 1.99, 95%CI: 1.20–3.31, P = 0.008; AG + AA vs. GG: OR = 1.41, 95%CI: 1.07–1.86, P = 0.016), and rs2296147 was also associated with increased cancer risk (CC vs. TT: OR = 2.17, 95%CI: 1.04–4.54, P = 0.039; CC vs. CT + TT: OR = 2.26, 95%CI: 1.09–4.69, P = 0.028). In a stratified analysis, rs751402 (AG + AA vs. GG: OR = 1.44, 95%CI: 1.02–2.02, P = 0.037) and rs2296147 (CC vs. CT + TT: OR = 2.33, 95%CI: 1.00–5.44, P = 0.050) were also found to be associated with diffuse-type GC risk. The most common GT haplotype (rs751402–rs2296147) showed protective effect for GC development (OR = 0.73, 95%CI: 0.58–0.91, P = 0.005), and especially for diffuse-type GC (OR = 0.68, 95%CI: 0.52–0.90, P = 0.006). Genetic effects on increased GC risk seemed to be enhanced by Helicobacter pylori infection, smoking and alcohol drinking, with corresponding adjusted ORs of 4.57, 2.42 and 2.50 for the rs751402 AG/AA variants, and of 5.32, 3.20 and 6.87 for the rs2296147 CC variant, but their interaction effects on GC risk didn't reach statistically significance. ERCC5 rs751402 and rs2296147 polymorphisms might alter the risk of developing GC and especially the diffuse subtype. Further validation of our results in larger populations and additional studies evaluating their function impact are required.     

Insulin-like growth factor axis gene polymorphisms modify risk of pancreatic cancer

Objective: Insulin-like growth factor (IGF)-axis genes plays a critical role in cancer development and progression via their impact on the RAS/MAPK/ERK and PI3 K/AKT/mTOR signaling pathways. We hypothesized that IGF-axis genetic variants modify individual susceptibility to pancreatic cancer. Methods: We retrospectively genotyped 41 single-nucleotide polymorphisms of 10 IGF-axis genes (IGF1, IGF2, IGF1R, IGF2R, IGFBP1, IGFBP3, IGFBP5, IRS1, IRS2, and IRS4) in 706 pancreatic cancer patients and 706 cancer-free controls using Sequenom and TaqMan technology. The association between genotype and pancreatic cancer risk was evaluated using multivariate logistic regression. A P value ≤.007 at a false discovery rate of 10% was set as the significance level. Results: We observed that the IGF1 *10212C>A and Ex4+2776G>A and IGF1R IVS2?70184A>G and IVS2+46329T>C variant genotypes were significantly associated with decreased pancreatic cancer risk (odds ratio [OR] range, 0.60–0.75) and that IGFBP1 Ex4+111A>G (I253M) was significantly associated with increased pancreatic cancer risk (OR = 1.46) after adjusted for other risk factors and multiple comparisons (P ≤ .007). IGF2R and IGFBP3 variant haplotypes were associated with increased and decreased pancreatic cancer risk, respectively (P < .001). We also observed a weak interaction of the IGF1R IVS2+46329T>C and IGF2R Ex45+11C>T (L2222L) genotypes with diabetes (P_interaction = .05) and interaction of IGF2R and IRS1 genotypes with alcohol consumption (P_interaction = .03 and .019, respectively) on increased pancreatic cancer risk. Conclusion: These findings support our hypothesis that polymorphic variants of IGF-axis genes act alone or jointly with other risk factors to affect susceptibility to pancreatic cancer.     

Association between IL13 gene polymorphisms and susceptibility to cancer: A meta-analysis

Background/aims

Interleukin-13 (IL13) is an immunoregulatory cytokine which plays an important role in carcinogenesis through affecting tumor immunosurveillance. Many studies had reported the influence of IL13 rs1800925 and rs20541 polymorphisms on cancer risk, however, with inconclusive results. The aim of the present study was to conduct a meta-analysis to clarify the relationship.

Methods

Twenty studies including a total of 6713 cancer cases and 8693 controls for IL13 rs20541 polymorphism and 4081 cancer cases and 6202 controls for IL13 rs1800925 polymorphism were included in the meta-analysis. Data were extracted from these studies and odds ratios with corresponding 95% confidence intervals were computed to estimate the strength of the association.

Results

Overall, the IL13 rs20541 polymorphism were associated with significantly decreased cancer risk in all genetic models (AA vs. GG: OR = 0.82, 95%CI = 0.71–0.95; GA vs. GG: OR = 0.92, 95%CI = 0.85–0.99; GA/AA vs. GG: OR = 0.90, 95%CI = 0.85–0.97; AA vs. GG/GA: OR = 0.85, 95CI% = 0.74–0.98). In the stratified analyses, significant effects were found among European populations, studies with population-based controls and studies of glioma. No influence of the IL13 rs1800925 polymorphism on the overall cancer risk was observed. However, in the stratified analyses, we found the IL13 rs1800925 polymorphism was significantly associated with decreased risk for glioma (CT vs. TT: OR = 0.72, 95%CI = 0.55–0.93; CT/TT vs. TT: OR = 0.76, 95%CI = 0.62–0.89).

Conclusion

Our meta-analysis suggests that the IL13 rs20541 polymorphism contributes to susceptibility to cancer, especially for glioma; and the IL13 rs1800925 polymorphism may be associated with glioma risk.     

Association of matrix metalloproteinases-9 gene polymorphisms with genetic susceptibility to esophageal squamous cell carcinoma

Matrix metalloproteinases-9 (MMP-9) plays important roles in tumor invasion and metastasis by degrading extracellular matrix components. Variations in the DNA sequence in the MMP-9 gene may lead to altered MMP-9 production and/or activity, and so this may modulate an individual's susceptibility to esophageal squamous cell carcinoma (ESCC). To test this hypothesis, we investigated the association of the MMP-9 polymorphisms and their haplotypes with the risk of ESCC in a Chinese population. There were significant differences in the genotype and allele distribution of P574R polymorphism of the MMP-9 gene among cases and controls. The P574R GG genotypes were associated with a significantly increased risk of ESCC as compared with the CC genotypes (odds ratio [OR] = 4.08; 95% confidence interval [CI]: 1.58-10.52; p = 0.00). Compared with 279R-574P haplotype, 279R-574R (OR = 3.52; 95% CI: 1.99-6.25) and 279Q-574P (OR = 2.16; 95% CI: 1.07-4.35) haplotypes can increase the onset risk of ESCC statistically, but the role of 279R-574R haplotype is more obvious. MMP-9 P574R polymorphisms and P574R-R279Q haplotype are significantly associated with the risk of ESCC. Our study shows for the first time that MMP-9 gene P574R polymorphism may contribute to a genetic risk factor for ESCC in a Chinese population.     

Association of CDKN1B gene polymorphisms with susceptibility to breast cancer: a meta-analysis

A number of case–control studies have been conducted to investigate the association of CDKN1B gene polymorphisms with breast cancer. However, these studies reported conflicting results. The aim of our study was to quantitatively summarize the association of CDKN1B gene polymorphisms with breast cancer. Systemic searches of the PubMed, Excerpta Medica Database, and Chinese Biomedical Literature Database databases were performed, with the last report up to Oct 2012. Odds ratios (ORs) with 95 % confidence intervals (CIs) were used to assess the strength of the association. Seven studies including 6,822 cases and 7,186 controls were involved in this meta-analysis, which was performed for two CDKN1B gene polymorphisms (rs2066827 and rs34330). Significant association was found for rs34330 polymorphism (T versus C: OR = 1.10, 95 % CI = 1.03–1.18, P = 0.003; CT + TT versus CC: OR = 1.38, 95 % CI = 0.98–1.93, P = 0.07; TT versus CC + CT: OR = 1.06, 95 % CI = 0.93–1.21, P = 0.38; TT versus CC: OR = 1.23, 95 % CI = 1.04–1.45, P = 0.02; CT versus CC: OR = 1.42, 95 % CI = 0.97–2.09, P = 0.07), but not for rs2066827 polymorphism (G versus T: OR = 0.99, 95 % CI = 0.91–1.08, P = 0.84; TG + GG versus TT: OR = 0.98, 95 % CI = 0.89–1.08, P = 0.69; GG versus TT + TG: OR = 1.04, 95 % CI = 0.83–1.30, P = 0.75; GG versus TT: OR = 1.03, 95 % CI = 0.82–1.30, P = 0.77; TG versus TT: OR = 0.97, 95 % CI = 0.88–1.08, P = 0.58). This meta-analysis suggests that breast cancer may be associated with CDKN1B gene rs34330 polymorphism, but not rs2066827 polymorphism.     

Role of xenobiotic metabolizing gene polymorphisms in breast cancer susceptibility and treatment outcome

Metabolic activation and inactivation of potential genotoxic agents occur by Phase I and Phase II enzymes in multiple interactions. An expanding body of literature demonstrates that ethnic differences in breast cancer incidence may be partly caused by host genetic factors particularly genetic polymorphisms of these carcinogen-metabolizing enzymes. The present case-control study aimed at identification of such low penetrance breast cancer susceptibility genes in 224 Indian women and to investigate the potential effects of their polymorphisms on sporadic breast cancer risk. The main objective of the study was to evaluate the effects of genetic polymorphisms of the xenobiotic metabolizing genes CYP1A1, GSTM1 and GSTT1 on breast cancer risk by PCR-RFLP and DNA sequencing. Our results showed a significant association between CYP1A1 m1, m2 polymorphisms and breast cancer risk; however there was a lack of association between GSTM1 null deletion and breast cancer. The associations of CYP1A1, GSTM1 and GSTT1 genotypes with breast cancer risk were more pronounced among the pre-menopausal patients. Combined genotype analysis revealed the CYP1A1 m2 ValVal-GSTM1 homozygous null deletion genotype combinations to be associated with the highest risk of breast cancer (OR=10.3, 95% CI=1.2-86.1). Correlations with clinicopathological factors and treatment outcome were also analyzed for predicting disease free survival by univariate and multivariate analysis. Significant differences in disease free survival between the wild and polymorphic genotypes were observed only for CYP1A1 m2, GSTT1 genotypes. Our results based on the analysis of functionally relevant polymorphisms in these low penetrance genes may provide a better model that would exhibit additive effects on individual susceptibility to breast cancer. Such genotype analysis resulting in a high-risk profile holds considerable promise for individualizing screening and therapeutic intervention in breast cancer. Hence, the present study may provide strong supportive evidence for genetic interactions in the etiology of breast cancer.     

Relationship between γ‐interferon gene polymorphisms and susceptibility to brucellosis infection

Interferon‐gamma (IFN‐γ) is a pro‐inflammatory cytokine that plays a pivotal role in the defense mechanism against Brucella infection. It was hypothesized that the IFN‐γ in (+874 A/T in intron 1) TT and +5644 T/A, TT genotypes, which are reportedly associated with high IFN production, are associated with susceptibility to brucellosis in Iranian subjects. Genotyping of these IFN‐γ variants by an allele‐specific polymerase chain reaction method was performed in 281 subjects, comprising 153 patients with active brucellosis and 128 healthy controls. It was found that the +874 minor allele (A) and homozygote genotype (AA) were significantly more frequently present in brucellosis patients than in controls (OR = 2.588; 95% CI, 1.313–5.104; P = 0.006 for the AA genotype; OR = 1.575; 95% CI, 1.124–2.216; P = 0.010 for the A allele). However, the allelic and genotypic distribution of the IFN‐γ polymorphism at position UTR5644 A>T did not differ significantly between patients and controls (P > 0.05). The distribution of haplotypes in this study suggests that the T/A haplotype (+874/UTR5644), which was present more frequently in controls than in patients, may protect subjects against Brucella infection. It is suggested that IFN‐γ +874 AA genotype and A allele are risk factors for developing brucellosis infection in Iranian subjects.