Serological analysis consisted of a seven antibody panel, and DNA was tested for CD-associated NOD2 variants (rs2066845,rs2076756,rs2066847), ATG16L1 (rs3828309, rs2241880) and IL23R (rs11465804).
Moreover, genome-wide association studies have revealed that variants of the gene encoding the IL-23 receptor, as well as the locus harboring the gene encoding the p40 chain, confer genetic risk for developing Crohn's disease (CD) and ulcerative colitis (UC).
We confirmed the role of IL23R and ATG16L1 in the CD susceptibility in the Czech population, and found a weak protective effect of IL23R p.381Gln against upper gastrointestinal tract involvement.
Colon-only CD (n = 228) was compared with healthy controls: three of six UC SNPs (in MST1, HLA-DRA, and IL-23R) and 11 of 34 CD SNPs: in IRGM, NOD2 (rs2066845), CCNY, MST1, IL23R, PTPN22, C11orf30, ZNF365, PTPN2, PSMG1, and rs1456893 were significantly associated.
Recently, positive association of CD with the variants in interleukin 23 receptor (IL23R), autophagy-related 16-like 1 (ATG16L1) genes and chromosome 5p13.1 locus was reported through genome-wide association studies which are now recognised as a robust tool for the identification of susceptibility genes for complex diseases.
Genotyping included CARD15/NOD2 variants p.Arg702Trp, p.Gly908Arg, and p.Leu1007fsX1008 and polymorphisms in SLC22A4/OCTN1 (1672 C-->T) and SLC22A5/OCTN2 (-207 G-->C) as well as 10 CD-associated IL23R variants.
In Crohn's disease (CD), such studies not only confirm the importance of caspase-activated recruitment domain 15 and major histocompatibility complex II molecules, but also reveal strong associations with the proinflammatory cytokine interleukin-23 receptor and autophagy-related 16-like gene.
A total of 438 individuals (143 with pediatric-onset CD [age <18 years], 139 with adult-onset CD, and 157 control subjects) evaluated for age at onset and disease location were genotyped for the R381Q mutation in the IL-23 receptor gene by pyrosequencing.
Additional suggestive associations (P < 4.2 × 10(-5)) were observed between Crohn's disease and IBD and African-specific SNPs in STAT5A and STAT3; between IBD and SNPs in IL23R, IL12B, and C2orf43; and between ulcerative colitis and SNPs near HDAC11 and near LINC00994.
We identify low frequency coding variants conferring protection against inflammatory bowel disease in IL23R, but we conclude that rare coding variants in positional candidates do not make a large contribution to inherited predisposition to Crohn's disease.
DNA was tested for three CD-associated NOD2 variants (3020insC, G908R, R702W), variants in IRGM, ATG16L1, IL12B, IL23R, STAT3, and a TLR5-stop mutation.
Our results confirm associations between IL12B and IL23R and psoriasis in Caucasians, and provide a genetic basis for the clinical association between psoriasis and Crohn's disease.
We replicated the previously reported associations between CD and rs11209026 and rs2241880, confirming that IL23R and ATG16L1 are susceptibility loci for CD in the New Zealand population.