Tu1882 FC Gamma Receptors Modulate the Inhibitory Efficacy of Infliximab in Blocking TNF-Mediated Responses in Blood and Intestine of IBD Patients

Abstract

Background & Aims: Tumor necrosis factor (TNF) is an important cytokine in the pathogenesis of inflammatory bowel disease (IBD). Anti-TNF drugs have been implemented in IBD therapy. The efficacies of those drugs differ among individuals and they have not been tested in different tissues. The aim of this study was to evaluate their efficacies in ex vivo-treated perhipheral blood and intestine of both IBD patients and healthy individuals. Methods: Peripheral blood obtained from healthy donors and IBD patients was used for stimulation experiments with anti-TNF drugs. Peripheral blood mononuclear cells (PBMCs) were isolated and the efficacies of anti-TNFs were assessed by RT-PCR and ELISA. Expression levels of Fc receptors were examined by Western blotting and RT-PCR. To determine the activation of Fc receptors we measured the production of GM-CSF and CCL-2 mRNAs and phosphotyrosine signal in THP-1 cells. The expression levels of Fc receptors in human intestinal tissues and in PBMCs were determined by RT-PCR and Western blotting. Results: Both adalimumab (ADA) and infliximab (IFX) displayed significant limitations in blocking TNFmediated responses in ex vivo-treated peripheral blood from healthy donors as compared to certolizumab-pegol (CZP; p<0.001). ADA had significantly lower efficacy in PBMCs as compared to THP-1 cells (p<0.001), which was correlated with the increased expression levels of both low affinity Fc receptors CD16 and CD32. IFX, but no other anti-TNFs tested was less effective in peripheral blood of IBD patients as compared to healthy controls (p<0.05) when assessed by measuring the changes on mRNA levels of IL-8, TNF and ICAM as well as plasma release of IL-8 (p<0.05). These differences were correlated with an increase in mRNA levels of both low affinity Fc receptors CD16 and CD32 in PBMCs from IBD patients as compared to healthy individuals. In THP-1 cells IFX either alone or in complex with TNF, was more potent in activating Fc receptors as measured by the production of GM-CSF and CCL-2 mRNA (p<0.05). IFX/TNF but not ADA/TNF complexes induced IL8 mRNA production in THP-1 cells (p<0.05), which was accompanied by detection of distinct phospho-tyrosine signals. Increased colonic mRNA (p<0.05) and protein (p<0.001) expression levels of CD64 as well as mRNA levels of CD16 (p<0.001) were detected in inflamed tissues of IFX-non-responders as compared to IFX responders. These changes were correlated with elevated mRNA levels of cytokines regulating the expression of this receptor, namely GM-CSF (p<0.01) and IFN-γ (p<0.0001) as well as IL-8 (p<0.0001) and IL-6 (p<0.05). Conclusions: Fc receptors modulate the efficacy of IFX both exand In Vivo. These observations will help to optimize individual anti-TNF strategy in IBD patients with elevated systemic and local levels of Fc receptors.