A new study confirmed the involvement of three genetic variants, or mutations, of the interleukin-23A (IL-23A) gene, and one variant of its receptor IL-23R, in the risk of developing multiple sclerosis (MS) and other related inflammatory nervous disorders, together known as inflammatory demyelinating diseases (IDD). Details of this study, “Characterization of variations in IL23A and IL23R genes: possible roles in multiple sclerosis and other neuroinflammatory demyelinating diseases,” were published in Aging. Despite the significant advances made in understanding MS and other inflammatory nervous disorders, its causes and molecular mechanisms are still essentially unclear. A number of studies have shown that complex genetic and environmental factors are involved in the developmental process of inflammatory diseases, where the immune system plays a central role. Among the involved genes is IL-23A, a gene that coordinates the activity of immune cells when binding to it receptor IL-23R. Several variants of this gene have been linked to autoimmune diseases. Researchers examined sites of the gene IL-23A and its receptor, IL-23R, in a total of 206 Chinese patients with IDD, including 84 MS patients, and compared the results with those of 300 controls. Serum levels of IL-23A were also compared in different groups of patients with these variants. Researchers identified three mutations — rs2066808, rs2371494 and rs11575248 — in the IL-23A gene, and one variant, called rs1884444, in the IL-23R receptor, that are linked to the risk of developing MS or other IDD diseases. More importantly, the team found clear differences in the serum levels of IL-23A in MS patients, alterations that were mainly caused by the variants in that gene. This observation further supported the involvement of IL-23A in inflammatory nervous disorders. "The cytokine IL23A has important effects in the differentiation of pro-inflammatory cells, and these cells have been considered to be the main factors in the MS pathogenesis," the researchers wrote. Their work, by identifying three IL-23A variants that affected serum levels in MS patients, provides "new evidence for the importance of IL-23A and IL-23R in the pathogenesis of the MS disease and demonstrating the differences between MS and other demyelinating syndromes in pathogenesis." "As functional genetic variants within the IL-23A gene have significant impacts on the host immune response, they could be excellent candidate targets for genetic association studies," they concluded.