The Th17 cytokine IL-22 is expressed at high levels in CD and correlates with disease activity, offering a better separation between active and inactive CD than IL-6 and TNF-alpha.
The proinflammatory cytokine IL-6 seems to have an important role in the intestinal inflammation that characterizes inflammatory bowel diseases (IBDs) such as Crohn disease and ulcerative colitis.
This study evaluated the correlations between the Crohn's Disease Activity Index (CDAI), the Simple Endoscopic Score for Crohn's Disease (SES-CD), serum high-sensitivity C-reactive protein (hsCRP) (both phenotype and genotype) and interleukin-6 (IL-6), and fecal calprotectin and lactoferrin.
Using quantitative real-time polymerase chain reaction (RT-PCR), we measured the mRNA expression levels of key Paneth cell antimicrobial peptides (DEFA5, DEFA6, LYZ, PLA2G2A), inflammatory cytokines [interkelukin 6 (IL6) and IL8], and a marker of epithelial cell content, villin (VIL1) in 106 samples from both affected ileum (inflamed Crohn's disease cases, n = 44) and unaffected ileum (non-inflamed; Crohn's disease cases, n = 51 and controls, n = 11).
To investigate the influence of interleukin 6 (IL-6), collagen type 1alpha1 (COL1A1), and vitamin D receptor gene (VDR) single nucleotide polymorphisms (SNP) on BMD in patients with Crohn's disease.
There was also variation in the frequency of IL-6-174 and TNF-alpha-308 genotypes in the ulcerative colitis group compared with the Crohn's disease group (p= 0.01).
In the organ culture studies, 20-day-old fetal rat parietal bones were incubated for 96 h with CD or control serum, serum preincubated with a neutralizing antibody to each cytokine or a nonimmune immunoglobulin control, and with IL-6.
To evaluate the role of the IL-6 gene in IBD, a functionally relevant polymorphism in the promoter region (G/C at position -174) has been genotyped in 169 patients with Crohn's disease (CD), 133 patients with ulcerative colitis (UC) and 440 healthy controls by using restriction fragment length polymorphism (RFLP) analysis.
A modest increase in the frequency of the IL-6*G allele was noted in Crohn's disease (CD) patients (50%) and ulcerative colitis (UC) patients (46.1%) as compared to controls (39.8%, P = 0.025).
It was found that LP macrophages in Crohn's disease (CD) and ulcerative colitis (UC) display high levels of NF-kappa B DNA-binding activity accompanied by an increased production of interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF) alpha.
Our data suggest enhanced expression of mucosal IL-6 mRNA in CD and of IL-8 mRNA in UC by infiltrating mononuclear cells, indicating the distinct participation of each cytokine in the pathogenesis of UC and CD.
IL-6 transcripts were elevated only in active inflammatory bowel disease specimens, suggesting that IL-6-mediated immune processes are ongoing in the inflammatory mucosal environment of CD and UC.