IL-12B Gene Polymorphisms and IL-12 P70 Serum Levels Among Patients with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is one of the autoimmune diseases, where different polymorphisms in cytokine genes play a pathogenic role. IL-12 is now recognized as a critical cytokine in terms of regulating the balance between Th1 and Th2 cells. We investigated the role of single nucleotide polymorphisms (SNPs) (rs3212227 (A/C) and rs17860508 (CTCTAA/GC)) of the IL-12B gene in the genetic susceptibility to RA and in the severity of the disease. Six hundred and thirty-four Caucasian RA patients and 341 healthy matched controls were studied using PCR-RFLP method and high-resolution melting analysis. Concentration of IL-12 cytokine level in serum was evaluated using ELISA. The genotype frequency did not deviate from HWE in each examined group. Frequencies of the rs3212227 CC genotype were statistically higher in patients with RA compared with the healthy control group in both codominant and recessive models (P = 0.037; P = 0.04, respectively). The frequency of rs3212227 C allele also showed similar tendency (P = 0.07). IL-12 level in serum was significantly higher in RA group compared with control (P < 0.0001). We observed that increased IL-12 serum level was correlated with higher number of tender and swollen joints, ExRA presence and higher levels of haemoglobin, CRP and PLT. Also higher IL-12 level in serum was observed within RA patients with hypertension. Present findings indicated that IL-12p40 + 1188A/C polymorphism as well as IL-12p70 protein levels may be associated with RA in the Polish population.