Our findings not only confirmed the association of IL10/rs1800871 and IL23R-IL12RB2/rs924080 with BD but also identified 2 susceptibility single nucleotide polymorphisms in IL10 and IL23R-IL12RB2 (rs3024490 and rs12141431) with BD in Han Chinese.
Behçet's disease (BD) susceptibility had been associated with single-nucleotide polymorphisms (SNPs) in IL23R-IL12RB2, IL10, STAT4, or ERAP1 locus in Japanese, Turkish, Chinese, and other populations, but not in a Korean genome-wide association study (GWAS).
Of particular note, the results of this study suggest that the presence of HLA-B 51 and the absence of HLA-B35 can be regarded as laboratory risk factors of venous thrombosis in patients with Behçet's disease.
Significant association of HLA-Bw4 with isoleucine at amino-acid position 80 (HLA-Bw4-80I) was found in the HLA-B*51(-) German cohort of BD patients [p(c) = 0.0042, OR = 2.35, 95% CI 1.41 to 3.93) and in the Turkish patients in comparison to the respective controls [p = 0.025, OR = 2.17, 95% CI 1.09 to 4.31].
However, recent genome-wide association studies have confirmed that HLA-B*51 is primarily associated with BD and that there are multiple susceptibility loci other than HLA-B*51.
Non-HLA genetic associations such as endoplasmic reticulum aminopeptidase 1 (ERAP1), interleukin 23 receptor (IL23R) and IL10 variations suggest that BD shares susceptibility genes and inflammatory pathways with spondyloarthritis.
Our study indicates that functional TNF-α, IL10 genotypes or combined TNF-α, IL10 genotypes do not play a role in BS susceptibility in Turkish BS patients.
There is no evidence supporting the use of HLA-B*51 as a diagnostic or prognostic marker for BD, and more clinical data must be collected in addition to basic immunological studies to exploit the potential of HLA-B*51 as a biomarker for BD management.
Regarding the non-HLA genes, the three SNPs located in IL23R and one of the SNPs in IL10 were found to be significantly associated with susceptibility to BD in our population.
Therefore, although they were not statistically significant, our data were consistent with an association between ERAP1 and BD as well as with an epistatic interaction between ERAP1 and HLA-B in the Spanish population.
However, they are associated with two different vasculitides (HLA-B*51 in Behçet's disease and HLA-B*52 in Takayasu's arteritis (TAK)) and with major clinical and immunological differences.
Among these variants, the genetic variant associated with Behçet's disease in the <i>HLA-B</i>/<i>MICA</i> region, which tags <i>HLA-B*51</i>, is within novel long intergenic noncoding RNA transcripts that are exclusively expressed from the haplotype with the protective but not the disease risk allele.
Genetic studies have supported the strong association of human leukocyte antigen-B and Behçet's disease, and high production of tumour necrosis factor and low production of interleukin (IL)-10, which have led to therapy based on controlling these effects.
Treg and Th17 cell frequencies and Th17 RORγt expression were significantly elevated, and IL-10 concentration in Treg cell supernatants was significantly lower in BD patients than in controls.
A significant increased frequency of HLA-B(*)44 (P = 0.02; OR = 2.78; CI 95% = 1.1-7.7), HLA-B(*)52 (P = 0.02; OR = 5.33; CI 95% = 1.07-29.1), and HLA-B(*)56 (P = 0.003; OR = 4.19; CI 95% = 3.37-5.21) as well as HLA-DRB1(*)01 and HLA-DRB1(*)13 (p = 0.007; OR = 3.36; CI 95% = 1.22-9.27) was found in Mexican patients with Behçet's disease when compared to controls.
GWAS data confirmed the major role of HLA-B51 in Behçet's disease susceptibility, and the discovery of epistatic interactions between HLA-B51 and ERAP1 variants provided some hints about its possible pathogenic mechanisms.
The objective of the present study was to clarify the pathological roles of CCR1 and IL10 loci identified by previous BD genome-wide association studies (GWASs).
Along with human leukocyte antigen gene encoding B*51 (HLA-B*51) and areas including the major histocompatibility complex class I, genome-wide association studies have recognized numerous other BD susceptibility genes including those encoding interleukin (IL)-10, IL-12 receptor β 2 (IL-12RB2), IL-23 receptor (IL-23R), C-C chemokine receptor 1 gene, signal transducer and activator of transcription 4 (STAT4), endoplasmic reticulum aminopeptidase (ERAP1), and genes encoding killer cell lectin-like receptor family members (KLRC4-KLRK1).
Altered trimming of microbial and/or endogenous peptides by endoplasmic reticulum aminopeptidase 1 (ERAP1), presented by <i>HLA-B</i><sup>*</sup><i>51</i>, may play a key role in BD pathogenesis causing an alteration in T cell balance with downregulation of Tregs and expansion of Th1 and Th17.
Moreover, we need to determine allele-specific effects of ERAP1 variants in the context of HLA-B*51 and HLA-Cw*6, which are associated with Behçet's disease and psoriasis, respectively.