A novel susceptibility locus in the IL12B region is associated with the pathophysiology of Takayasu arteritis through IL-12p40 and IL-12p70 production.
Four single nucleotide polymorphisms (SNPs) those locate in the IL12B region (rs56167332), the MLX region (rs665268), the FCGR2A/FCGR3A locus (rs10919543), and the HLA-B/MICA locus (rs12524487), associated with TA in different population, were genotyped in 123 Chinese TA patients and 147 healthy controls from January 2013 to August 2014.
Our findings indicate that IL12B plays a fundamental role on the pathophysiology of TAK in combination with HLA-B(∗)52:01 and that common autoimmune mechanisms underlie the pathology of TAK and other autoimmune disorders such as psoriasis and inflammatory bowel diseases in which IL12B is involved as a genetic predisposing factor.
Outside the HLA region, only one polymorphism located nearby the IL12B gene surpassed the study-wide significance threshold in the meta-analysis of the discovery datasets (rs755374, P = 7.54E-07; OR<sub>GCA</sub> = 1.19, OR<sub>TAK</sub> = 1.50).
After getting evidence of IL12p40 encoded by IL12B as a possible therapeutic target by showing similarities of the genetic background between TAK and ulcerative colitis, we performed a pilot clinical study of ustekinumab, a monoclonal antibody against IL12p40 for patients with refractory TAK and obtained good response.
The frequencies of IL12B 1188 C allele (p = 0.03, OR = 1.7) and CC genotype (p = 0.007, OR = 3.7) were both higher in TA patients than in control subjects.
We demonstrated a allele association between the four SNPs of IL12B and TA (rs6871626: OR 1.52, 95% CI 1.26-1.83; rs4921492: OR 1.46, 95% CI 1.21-1.75; rs60689680: OR 1.41, 95% CI 1.17-1.69; rs4921493: OR 1.45, 95% CI 1.21-1.75, all P <sub>c</sub> < 10<sup>- 3</sup> ).
Since TAK and UC share HLA-B*52:01 and IL12B as genetic determinants, and since there are case reports of the co-occurrence of these diseases, we hypothesized that UC is a common complication of TAK.
We investigated the linkage between presumptive TA-related genes (FCGR2A/FCGR3A, EEFSEC, RPS9/LILRB3, RIPPLY2 and MLX) and TA in the Han Chinese population.We performed a large case-control multi-center study of 412 Han Chinese TA patients and 597 ethnically matched healthy controls.
Four single nucleotide polymorphisms (SNPs) those locate in the IL12B region (rs56167332), the MLX region (rs665268), the FCGR2A/FCGR3A locus (rs10919543), and the HLA-B/MICA locus (rs12524487), associated with TA in different population, were genotyped in 123 Chinese TA patients and 147 healthy controls from January 2013 to August 2014.
Sera from AAECA-positive patients with TA, compared with sera from AAECA-negative patients with TA and that from controls, induced increased expression of E-selectin (mean +/- SD 0.833 +/- 0.063 versus 0.217 +/- 0.081 and 0.221 +/- 0.101 optical density [OD] units, respectively) and vascular cell adhesion molecule 1 (0.620 +/- 0.144 versus 0.165 +/- 0.005 and 0.177 +/- 0.055 OD units, respectively) and increased production of interleukin-4 (IL-4) (6.8 +/- 2.4 versus 1.2 +/- 1.6 and 1.3 +/- 2.5 pg/ml, respectively), IL-6 (24.3 +/- 2.4 versus 4.5 +/- 6.7 and 5.9 +/- 5.1 pg/ml, respectively), and IL-8 (36.8 +/- 10.3 versus 10.1 +/- 6.7 and 7.8 +/- 2.1 pg/ml, respectively).
Although no definite boundaries exist, it may be suggested that the IL-6/Th17/IL-17 pathway primarily drives systemic inflammation while the IL-12/Th1/IFN-γ pathway dominates in vascular wall inflammation both in TAK and giant cell arteritis.
IL-6 levels in TAK patients were significantly increased irrespective of disease phase, while a significant increase in sIL-6R concentrations was only found in TAK patients with active disease.
The polymorphism of IL-12 as well as IL-6 and IL-2 genes may contribute to susceptibility and pathogenesis of TA by altering cytokine production and inducing inflammation.
Serum IL-6 seems to be the best biomarker for disease state and disease activity in TA and increased Th1 and Th17 responses are predominant in the pathophysiology of TA.
We identified genetic susceptibility loci for Takayasu arteritis with a genome-wide level of significance in IL6 (rs2069837) (odds ratio [OR] 2.07, P = 6.70 × 10(-9)), RPS9/LILRB3 (rs11666543) (OR 1.65, P = 2.34 × 10(-8)), and an intergenic locus on chromosome 21q22 (rs2836878) (OR 1.79, P = 3.62 × 10(-10)).
Taken together with possible involvement of interleukin-6 in the pathogenesis of heart failure and muscle wasting, inhibition of interleukin-6 receptor signalling by tocilizumab may be a safe and reasonable approach in the treatment of active TA with heart failure and muscle wasting.