HLA-G is expressed in intestinal samples of ulcerative colitis and Crohn's disease patients and HLA-G5 expression is differentially correlated with TNF and IL-10 cytokine expression

HLA-G is an immunomodulatory molecule that can be produced by epithelial cells. Considering that TNF and IL-10 participate in bowel inflammatory disorders and that both cytokines modulate HLA-G, we evaluated HLA-G, TNF and IL-10 mRNA expression by qPCR and HLA-G protein levels by immunohistochemistry in two intestinal samples exhibiting different degree of inflammation within a patient suffering from Crohn's disease (CD) or ulcerative colitis (UC). Tissue HLA-G5 (P < 0.0001), TNF (P = 0.0004) and IL-10 (P = 0.0169) mRNA expression levels were higher in intestinal areas exhibiting intense inflammation compared to areas of low inflammation, and HLA-G protein levels were not associated with degree of mucosal inflammation. In CD, the expression of TNF was correlated with IL-10 in low inflamed areas, exhibiting a TNF:IL-10 ratio = 3, but in inflamed areas the ratio increased to 9-folds. In UC, the expression of TNF was correlated to IL-10, irrespective of the inflammation grade, with little variation of the TNF:IL-10 ratio in the various inflamed areas. TNF and IL-10 expression was correlated with HLA-G5 expression in mild inflamed areas. Both CD and UC samples exhibited gene and protein expression of HLA-G; and the HLA-G5 expression is differentially correlated with TNF and IL-10 levels depending on the type of the underlying inflammatory bowel disorder.