P164 HLA G expression is differentially expressed in infiltrating cells in inflammatory bowel disease and in healthy specimens

Abstract

Background Since HLA-G is an immune checkpoint molecule and since Crohn’s disease (CD) and ulcerative colitis (UC) exhibit immune-mediated mechanism deregulation, we aimed to evaluate HLA-G intestinal expression and soluble (sHLA-G) levels in CD/UC patients, stratified according to CD phenotype/localisation and UC extension. Methods HLA-G tissue expression was assessed by immunohistochemistry in biopsies collected from 151 patients (90 CD, 61 UC) and 24 healthy controls, and in surgical resections (28 CD, 12 UC). Plasma sHLA-G levels (97 CD, 81 UC and 120 controls) were evaluated using ELISA Results HLA-G expression was observed in intestinal epithelial cells of controls and CD/UC specimens, exhibiting closely similar profiles, and in lamina propria infiltrating cells, exhibiting differential patterns. In biopsies, CD/UC lamina propria plasma cells/lymphocytes presented: i) increased HLA-G expression compared with controls (p < 0.0001), ii) irrespective of the extent, UC cell staining was greater compared with CD cells (p = 0.0011), and iii) the inflammatory CD phenotype presented increased number of infiltrating cells compared with stenosing and fistulizing phenotypes (p = 0.0407). In surgical resections, CD/UC patients exhibited increased infiltrating cell HLA-G expression in lesion areas compared with margins. sHLA-G levels were increased in UC/CD patients (p < 0.0001) when compared with controls, but no difference was observed between patients. Conclusion Increased infiltrating cell HLA-G expression associated with increased sHLA-G levels in CD/UC patients may reflect host on-going strategies to suppress chronic inflammation. References