The Impact of Promoter Variants in Interleukin-18 on Susceptibility to Ankylosing Spondylitis in a Sample of Iraqi Patients

<ns3:p> Background Ankylosing spondylitis (AS) is a chronic inflammatory illness mainly influencing the axial skeleton. It is a multifactorial illness in which environmental and genetic parameters contribute to its cause, one of which is interleukins, including interleukin-18 (IL-18). Therefore, this study aimed to investigate the association between single nucleotide polymorphism (SNP) rs549908 and serum levels of IL-18 in Iraqi patients with AS. Methods During the period of November 2024 and January 2025, a total of 100 individuals were enrolled in the present work, including 50 patients with AS and 50 healthy controls (HC), were obtained from Baghdad Teaching Hospital. Using enzyme-linked immunosorbent assay (ELISA) and TaqMan real-time polymerase chain reaction (PCR), serum levels and rs549908 genotyping of IL-18 were estimated. Results Significantly, levels of IL-18 in serum were raised in patients with AS compared to HC (235.7060 <ns3:italic>vs.</ns3:italic> 151.10 pg/mL, p < 0.001). Genetically, T allele frequency (69.0% vs. 49.0%, <ns3:italic>p =</ns3:italic> 0.006) and TT genotype frequency (53.1% vs. 23.5%, <ns3:italic>p =</ns3:italic> 0.004) were significantly greater in patients with AS compared to HC. Analysis under the model of dominant (TG + GG <ns3:italic>vs.</ns3:italic> TT) demonstrated significant association between status of illness and genotype (OR = 0.29, <ns3:italic>p =</ns3:italic> 0.007). Conclusions These outcomes suggest rs549908 SNP and serum levels of IL-18, are related with increased susceptibility to AS in the Iraqi population. </ns3:p>