ss article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. *Corresponding Author: Gülay Börekçi, Mersin University, Institute of Health Science, Department of Molecular Microbiology, Mersin, Turkey. E-mail: gulay_borekci@yahoo.com Phone: +90 532 722 67 12 Received: Apr, 2020. Accepted: Dec, 2020. Journal of Immunology and Clinical Microbiology © 2020 Original Article J Immunol Clin Microbiol. 2020;5(4):123-132 Investigation of the Relationship Between TNF-α, IL-12A, IL-12B and IFN- γ Gene Polymorphisms and Chronic Hepatitis B in Turkish Populations Gülay Börekçi1,2* , İrem Bekalp Yılmaz3, Özlem Kandemir4, Ayşegül Çetinkaya3, Gülhan Orekici Temel5, Nurcan Aras3 1 Mersin University, Institute of Health Science, Department of Molecular Microbiology, Mersin, Turkey. 2 Mersin University, Faculty of Nursing, Department of Nursing Management, Mersin, Turkey. 3 Mersin University, Faculty of Medicine, Department of Medical Biology, Mersin, Turkey. 4 Mersin University, Faculty of Medicine, Department of Clinical Microbiology and Infectious Diseases, Mersin, Turkey. 5 Mersin University, Faculty of Medicine, Department of Biostatistics, Mersin, Turkey. J Immunol Clin Microbiol Abstract: Introduction: This study aimed to determine the relationship between TNF-α (-1031 T/C), IL-12A (3'UTR G/A), IL-12B (3'UTR A/C) and IFN-γ (+874 A/T) gene polymorphisms and chronic hepatitis B infections. Materials and Methods: 100 patients with chronic hepatitis B and 100 healthy subjects were included in this study. Approximately 2 ml of peripheral blood from patient and control groups were taken into tubes with EDTA and the genomic DNA was isolated by using the DNA isolation kit. Single nucleotide polymorphisms (SNPs) in TNF-α (-1031 T/C), IL-12A (3'UTR G/A), IL-12B (3'UTR A/C) and IFN-γ (+874 A/T) genes were investigated by using RT-PCR method. Results: It was determined that there was no statistically significant difference in terms of the allele and genotype frequencies of TNF-α (T/C) and IFN-γ (A/T) between chronic hepatitis B patients and the control group (p>0.05). However, there was a statistically significant difference between the patient and control groups for IL-12A (G/A) and IL-12B (A/C) in terms of genotype and allele distributions. The frequencies of IL-12A GG and GA genotypes (OR: 0.814, 95% 0.369-1.795, p=0.001) in patient group, and AA genotype in control group (OR: 2.608 95% 1.189-5.720, p=0.001) were high. Futhermore, it was found that the frequencies of IL-12A G allele in patient group and A allele in control group (OR: 1.981, 95%1.115-2.462, p=0.001) were high. In terms of IL-12B genotype and allele distributions, the frequencies of AC genotype (OR: 0.131, 95% 0.049-0.350, p=0.001) and A allele was higher in patient group than control group, whereas C allele in the control group was high. (OR:1.657, 1.115-2.462, p=0.012). Conclusions: Our results showed that TNF-α (-1031 T/C), and IFN-γ (+874 A/T) polymorphism is not effective in chronic HBV infections. However, IL-12A (3'UTR G/A) and IL-12B (3'UTR A/C) polymorphisms may influence the chronicity of hepatitis B.