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* = Presenting author

P033 Anti-TNF-α therapy normalises aberrant cytokine production and homing profile of circulating dendritic cells in Crohn’s disease

P. Hendy*1, 2, D. Reddi2, D. Bernardo3, L. Durant2, A. Noble2, N. English2, S. Knight2, A. Hart1

1St Mark’s Hospital, Gastroenterology, LONDON, United Kingdom, 2Imperial College, Antigen Presentation Research Group, London, United Kingdom, 3Hospital Universitario de La Princesa, Department of Immunology, Madrid, Spain

Background

Crohn’s disease is characterised by a dysregulated T lymphocyte response to mucosal antigens. Human circulating dendritic cells (DC) migrate to target tissue lymph nodes where they present antigens and stimulate either an inflammatory or a tolerogenic T-cell response. In Crohn’s disease, DC are likely to contribute to inflammation through regulation of T-cell responses. Potential options for DC modification (from pro-inflammatory to pro-tolerant) include in-vivo therapy or in-vitro modulation of harvested DC followed by autologous transplant. However, the phenotype, function, and response to therapy of peripheral blood DC in Crohn’s disease remain poorly described.

The aims of our study were to fully characterise the blood myeloid DC (mDC) and plasmacytoid (pDC) phenotype (including homing, maturation, and pattern-recognition receptor [PRR] status) and ongoing cytokine production in Crohn’s disease, and to assess the ex-vivo effect of the anti-TNF-α agent infliximab on DC.

Methods

Blood was taken from 13 adult patients with luminal Crohn’s disease before and 6 weeks after commencement of infliximab and from matched healthy controls. DC were identified within the peripheral blood mononuclear cells by flow cytometry as HLA-DR positive and lineage (CD3/CD14/CD16/CD19/CD34) negative and further described as mDC (CD11c+ CD123-) and pDC (CD11c- CD123+). Expression of homing markers (β7 [gut], CLA [skin]), PRR (TLR2 &4) and activation markers (CD40, CD80, CD86, and ILT3) were studied. In addition, ongoing assessment of DC cytokine production (TNF-α, INF-α, IL-1β, IL-6, IL-10, IL-12, IL-23, and TGF-β) was performed over 4 hours with monensin.

Results

The homing profile of mDC was abnormal in Crohn’s disease, with a greater gut homing specificity (β7+ CLA- p = 0.0025) and a decreased proportion of non-tissue specific (β7+ CLA+ P = 0.0052) DC, which normalised with infliximab therapy (p = 0.048 and 0.014 respectively). Ongoing production of TNF-α by mDC and IL-6 by pDC was significantly increased in Crohn’s disease (p = 0.0035 and 0.0068, respectively) and decreased significantly with infliximab therapy (p = 0.032 and 0.0221, respectively).

Conclusion

The cytokine milieu has a vital role in determining the type of T-cell response generated to presented antigen. The abnormal DC cytokine production that we demonstrate here, indicative of Th17 pathway stimulation, is likely to be pivotal to the abnormal T-cell response in Crohn’s disease. The significant reduction in DC production of inflammatory cytokines and normalisation of DC homing markers following treatment suggests a central role for DC in restoring immune homeostasis in Crohn’s disease, and highlights their potential as a therapeutic target.