Интерлейкин 6 (ИЛ-6, Interleukin 6, IL-6)

The Interleukin 6 (IL6) -174G>C promoter polymorphism test (also known as the IL-6 promoter variant or IL6 -174G>C genotyping) assesses inherited differences in IL6 gene regulation that influence interleukin-6 expression. This assay supports risk assessment and research-focused evaluation of conditions linked to IL-6–mediated inflammation and endocrine signaling, rather than diagnosing any disorder. Associations described in the literature include earlier onset of type 1 diabetes, dyslipidemia, hyperandrogenic states in women, lower bone mineral density/osteoporosis, growth failure in pediatric Crohn disease, juvenile rheumatoid arthritis, Kaposi sarcoma in men with HIV infection, and hemorrhagic presentation among patients with cerebral arteriovenous malformations.

Interleukin-6 (IL-6) is a pleiotropic cytokine central to innate and adaptive immune responses. It induces acute-phase protein synthesis, modulates endocrine pathways by stimulating vasopressin and growth hormone secretion, activates the hypothalamic–pituitary–adrenal axis, and suppresses thyroid function. IL-6 also exerts thermogenic effects, promotes neuronal differentiation, stimulates hepatocytes, and drives B- and T-lymphocyte proliferation and differentiation. Circulating IL-6 commonly increases with severe inflammation, infection, and tissue injury, and it contributes to the pathophysiology of osteoporosis, rheumatoid arthritis, and malignancy. The IL6 gene encodes IL-6. A functional promoter variant at position −174 (G→C; −174G>C) alters transcriptional regulation. The C allele is associated with reduced IL6 expression, and unlike the G allele, shows minimal inducibility by lipopolysaccharide and interleukin-1. Genotype–expression relationships reported include: G/G—relatively higher IL6 expression; G/C—reduced expression; C/C—markedly reduced expression. Because this assay interrogates a polymorphism, there is no concept of “normal” or “pathologic” result; findings require correlation with other genetic data and clinical context. Multiple phenotype associations have been reported. In men with HIV infection, the G/G genotype correlates with higher lifetime risk of Kaposi sarcoma, whereas C/C appears protective. Carriers of the G allele show nearly twofold higher triglycerides, very-low-density lipoproteins, and free fatty acids compared with C-allele carriers, supporting a role in dyslipidemia. Among healthy women, the combination of G at −174 and G at −597 associates with higher circulating IL-6 and higher basal cortisol, 11-deoxycortisol, and 17-hydroxyprogesterone, consistent with links to hyperandrogenic conditions. Fewer protective C alleles at IL6 promoter sites (−572 and −174) associate with higher C-reactive protein (up to +79%) and bone resorption markers (up to +32%), alongside a trend toward reduced lumbar spine bone mineral density. The C/C genotype associates with earlier onset of type 1 diabetes. In pediatric Crohn disease, G/G associates with greater growth delay and higher IL-6–induced inflammatory activity (C-reactive protein) compared with C/C or C/G. In patients with cerebral arteriovenous malformations, homozygosity for the G allele associates with increased risk of intracranial hemorrhage.