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P011. Anti-TNF-alpha induces a dysregulated tissue-homing profile on human immune cells in-vitro

S. Peake1, D. Bernardo2, E. Mann2, H.O. Al-Hassi2, J. Landy1, C. Tee2, S. Knight2, A. Hart1

1St Marks Hospital, IBD Unit, London, United Kingdom; 2Antigen Presentation Research Group, Imperial College, London, United Kingdom

Background: In health, the immune system maintains immune homeostasis in the gut. In inflammatory bowel disease (IBD), there is dysregulated immune activity resulting in mucosal inflammation. The inflammatory process may also involve other organs, such as the skin, eye, liver and joints (extra-intestinal manifestations, EIM). The cause of EIM is poorly understood. However compartmentalisation of inflammatory processes to specific organs may be linked to abnormalities in immune cell trafficking. Anti-TNF-alpha therapies are effective treatments for IBD, but their precise mechanism of action is unclear. Paradoxical skin inflammation (e.g. psoriasis, eczema) has been reported in up to 20% of patients treated with anti-TNF-alpha therapy. Antigen presenting cells (APC) and effector cells (T-cells) are involved in tissue homing. In this study, we investigated the in-vitro effect of anti-TNF-alpha on homing marker expression on peripheral blood mononuclear cells (PBMCs) from healthy subjects.

Methods: PBMCs were isolated from fresh blood from 8 healthy volunteers by performing a Ficoll gradient separation and cells were cultured in-vitro (1million PBMC/ml) with and without Infliximab (IFX, 100 µg/ml) at 37.0°C for 24 hours. Previous dosimetry studies had used 10 ng/ml, 1 µg/ml and 100 µg/ml. DC (HLA-DR+, CD3−, CD14−, CD16−, CD19−, CD34−, CD56−), monocytes (CD14+), T‑cells (CD3+) and B‑cells (CD19+) were identified by flow cytometry after culture. Expression of skin (CLA, CCR4, CCR10), gut (beta7, CCR9) and lymph node (CCR7) homing markers were quantified after culture. Paired t‑test was applied.

Results: Monocytes (macrophage precursors) cultured with IFX increased CCR7 expression (p = 0.023). T‑cells increased CCR4 (p = 0.043) and decreased CCR7 (p = 0.02) expression after culture with IFX. Expression of beta7 on T‑cells with IFX was also down-regulated but this did not reach statistical significance (p = 0.09). There were no significant differences in homing marker expression on DCs or B‑cell populations.

Conclusions: Up-regulation of CCR4 and reduced expression of beta7 on T‑cells incubated with IFX shows the acquisition of a skin-homing profile by T‑cells, suggesting a possible mechanism for paradoxical skin inflammation observed in patients treated with anti-TNF-alpha therapy. Increased expression of CCR7 on monocytes following incubation with IFX suggests an increased lymph node homing capacity, which may promote immune non-responsiveness. Targeting tissue-homing pathways provides a specific approach to IBD therapy.