Interleukin-35 (IL-35) is a member of the IL-12 family of heterodimeric cytokines produced by regulatory T (Treg) cells. This immunosuppressive cytokine can prevent exaggerated inflammatory responses like those responsible for the development of rheumatoid arthritis (RA). This study aims to determine the correlation between the gene expression of Epstein-Barr virus-induced gene 3 (EBI-3) and IL-12A (p35) subunits of IL-35 in peripheral blood leukocytes with immunological and clinical parameters in RA patients.
We recruited 47 patients with RA and 44 healthy subjects. The disease activity score-28 (DAS-28) was assessed by an expert rheumatologist and the plasma levels of neopterin and anti-cyclic citrullinated peptide (anti-CCP) was measured using ELISA method also Serum rheumatoid factor (RF) was assessed by the agglutination test. For the evaluation of IL-12A and EBI-3 gene expression, we used qPCR.
We did not find any significant correlation between the gene expression of IL-35 subunits and DAS-28. There was a negative correlation between the plasma levels of neopterin and the gene expression of EBI-3 (p = 0.004). Inversely, we found a positive correlation between plasma level of anti-CCP and neopterin (p < 0.001) also between RF and DAS-28 (p = 0.001).
Regarding the significant negative correlation between EBI-3 gene expression and plasma levels of neopterin, it can be concluded that the altered gene expression of EBI-3 may play a role in the pathogenesis of RA.