Recent studies have suggested that nucleotide-binding oligomerization domain 2 (NOD2)/caspase recruitment domain 15 (CARD15) gene single nucleotide polymorphisms (SNPs), implicated in innate immunity and Crohn's disease, may also affect immune function post-HSCT.
Mutations in the leucine-rich repeat (LRR) domain of Nod2 have been implicated in the pathogenesis of Crohn's disease, yet the function of Nod2 and regulation of the Nod2 pathway remain unclear.
In Tunisian population, the 3020insC insertion in NOD2/CARD15 gene is a marker of susceptibility to CD, while the A allele at position -627 in the IL-10 promoter increases the risk of CD ileal location and severe disease presentation.
The recently discovered NOD2 gene has been correlated to ileal location of Crohn's disease and subsequently could affect growth through the resulting phenotype or as an independent risk factor.
A frameshift mutation (Leu1007fsinsC) and two missense mutations (Gly908Arg and Arg702Trp) in the NOD2/CARD15 gene are strongly associated with susceptibility to Crohn's disease.
Dissection of the molecular events coupling CARD15 mutation to Crohn's disease has also been intensively investigated and, while not resolved as of yet, has significantly advanced understanding of the intestinal immune response to microbial challenge.
Despite this, recent studies reported variable associations between CD and CARD15 mutations in distinct ethnic groups, thus raising the hypothesis that genetic and/or allelic heterogeneity may influence the relationship between CARD15 and CD.
From the CARD15 gene mutations in the adult Crohn's disease population the 1007finsC, while in the pediatric population the 1007finsC and the G908R were significantly associated with an increased risk for Crohn's disease.
These findings thus define a mechanism of NOD2-mediated regulation of innate immune responses to intestinal microflora that could explain the relation of CARD15 polymorphisms and resultant NOD2 dysfunction to CD.
This study analysed variations of colonic lymphoid follicles (CLFs) according to the nucleotide-binding oligomerization domain 2 (NOD2) and caspase recruitment domain-containing protein 15 (CARD15) gene in patients with Crohn's disease.
Our findings reveal similar immunological aberrancies in CD in the general population as reported in CD patients with mutated intracellular bacterial sensor NOD2, namely attenuated activation of innate cytokines and impaired autophagy, combined with a reduced capacity to up-regulate the T helper type 17 (Th17) response.
Genotype-phenotype analysis demonstrated that CARD15 variants were associated with ileal disease (p=0.0006, OR = 9.3, CI = 2.2-34) and protective for colonic CD (p = 0.01, OR = 0.18).
Several combinations of genetic factors predisposing to CD have been described, with the most significant replicable associations including genes for intracellular receptors of bacterial cell walls (NOD2/CARD15) and for bacterial clearance and antigen processing via autophagy (ATG16L1 and IRGM).
We analyzed the NOD2 variants among admixed AAs (n = 321, 240 with CD and 111 healthy controls [HCs]) and nonadmixed West Africans (n = 40) by genotyping four known disease-causing NOD variants.