LAUSR

Despite an expanding array of treatment options, a significant proportion of patients with Crohn’s Disease (CD) fail to respond to currently available therapies, underpinning the importance of biological insights into disease pathogenesis. The pro-inflammatory chemokines CXCL9,10 and 11 bind to the CXCR3 receptor, highly expressed on effector T-cells. Mouse models of chronic ileitis have shown that CXCR3+ effector T cells drive the loss of paneth cells that play an important role in innate immunity and mucosal barrier function. In the TNFΔΔARE mouse ileitis-model, small molecule inhibition of the CXCR3 receptor reverses paneth cell loss and restores antimicrobial peptide levels. The aims of this study were to evaluate the role of chemokines that bind to CXCR3+ effector T-cells in adult patients with ileal CD compared to healthy controls and to assess the impact of these pro-inflammatory chemokines on paneth cell derived anti-microbial peptides. Methods, 13 CD patients and 16 healthy controls attending for routine endoscopic evaluation were prospectively recruited at St.Vincent’s University Hospital, Dublin and ileal biopsies were collected in media. RNA was isolated from homogenised ileal biopsies (Quiagen kit), DNAse treated using DNAse I (Invitrogen) and reverse transcribed using M-MLV reverse transcriptase (Promega). Target cDNAs were quantified using an Applied BiosystemsTM QuantStudioTM 7 Flex Real-Time PCR System. We identified an increase in the relative mRNA expression of CXCR3 associated chemokines, with significantly higher levels of CXCL9, CXCL10 and CXCL11 in ileal CD patients compared to healthy controls. This coincides with a reduction in paneth cell-derived antimicrobial peptides with significantly lower levels of alpha defensins (DEFA5, DEFA6) and lysozyme in CD patients compared to healthy controls. This study supports data from animal models and provides a hypothesis for the loss of paneth cells in patients with ileal CD. The reduction in paneth cell derived anti-microbial peptides may help to explain the altered microbiome and provide an explanation for the loss of mucosal barrier integrity in Inflammatory Bowel Disease (IBD). A greater understanding of the role of chemokines in the development of mucosal immunity and inflammation in IBD may allow the targeting of chemokines in novel therapeutic strategies.