Defb1, encoding human Beta Defensin-1 (hBD-1), is a key gene in the innate immune system. hBD-1 is an antimicrobial peptide involved in epithelial defence of various tissues, and polymorphisms within the DEFB1 gene could influence gene expression and protein production [10].

Multiple studies have explored the association between DEFB1 polymorphisms and various diseases. A meta-analysis showed that the DEFB1-G1654A polymorphism may be a genetic susceptibility factor for periodontitis [1]. However, no significant differences were found between DEFB1 rs11362, rs1799946 and rs1800972 and periodontitis [1]. Another meta-analysis indicated that DEFB1 rs11362 polymorphism may not have an important effect on the risk of chronic periodontitis [2].

In a Zambian population, DEFB1 polymorphisms were significantly associated with decreased risk of HIV-1 infection acquisition, suggesting a role in HIV-1 mother-to-child transmission [3]. In an Egyptian population, different DEFB1 gene polymorphisms may modify the risk of vitiligo development, the disease extent and the response to NB-UVB phototherapy [4]. A case-control study demonstrated that rs11362 A/G polymorphism of the DEFB1 gene is involved in the risk of developing coronary artery disease (CAD), with the rs11362 AA genotype associated with low mRNA expression of β-defensin-1 in heart tissue [5]. In a Chinese cross-sectional study, carriers of the DEFB1 rs11362 T allele had a higher risk of dental caries [6].

In Italian children, there was no significant correlation between most DEFB1 allele, genotype and haplotype frequencies and recurrent tonsillitis susceptibility, except for an increased risk in patients carrying DEFB1 rare haplotypes [7]. In a Brazilian population, no association was found between three studied DEFB1 polymorphisms and tuberculosis, though the sample size may have affected the results [8]. In prostate cancer cells, DNA methylation-mediated downregulation of DEFB1 occurs, as CpG methylation frequencies in the DEFB1 low CpG-content promoter were significantly higher in malignant tissues [9]. Also, polymorphisms in the DEFB1 gene at positions-52 and-44 were associated with hBD-1 salivary concentrations in healthy subjects [10].

In conclusion, Defb1, through its encoded hBD-1, plays a role in innate immune responses. Studies on its polymorphisms have revealed associations with diseases such as periodontitis, HIV-1 mother-to-child transmission, vitiligo, CAD, dental caries, and potentially recurrent tonsillitis and tuberculosis. These findings contribute to understanding the role of Defb1 in disease susceptibility and progression, and highlight the importance of studying gene polymorphisms in uncovering the gene's function in various biological processes related to disease.