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* = Presenting author

P026 Characterisation of mucosal CD4+ T-cells in peripheral blood of healthy controls and paediatric inflammatory bowel disease patients

M. Joosse*1, C. Menckeberg1, L. de Ruiter1, H. Raatgeep1, L. van Berkel1, F. Muskens2, R. Hendriks2, R. Hoogenboezem3, T. Cupedo3, L. de Ridder4, H. Escher4, S. Veenbergen1, J. Samsom1

1Erasmus MC, Laboratory of Paediatrics, division Gastroenterology and Nutrition, Rotterdam, Netherlands, 2Erasmus MC, Department of Pulmonary Medicine, Rotterdam, Netherlands, 3Erasmus MC, Department of Haematology, Rotterdam, Netherlands, 4Erasmus MC, Department of Paediatric Gastroenterology, Rotterdam, Netherlands

Background

We have shown that gut-imprinted mucosal T-cells express low levels of CD62L and high levels of CD38 on their surface when circulating in peripheral blood. This new CD4+CD62LnegCD38+ phenotype lowers the threshold for detection of circulating mucosal antigen-specific CD4+ T-cell responses. Responses can be compared with CD4+CD62LnegCD38neg cells (‘non-mucosal T-cells’) within the same individual. We hypothesise that during active inflammatory bowel disease (IBD) circulating mucosal T-cells may have a more activated phenotype when compared with mucosal T-cells in healthy controls, and we have therefore monitored these cells in healthy individuals and paediatric inflammatory bowel disease (PIBD) patients.

Methods

Transcriptome analysis of purified circulating mucosal T-cells and non-mucosal T-cells isolated from adult healthy donors (n = 3) was performed. To study T-cell function, purified mucosal and non-mucosal T-cells from adult healthy donors were co-cultured with allogeneic LPS-stimulated monocyte-derived dendritic cells, denoted as mixed lymphocyte reaction (MLR). T-cell responses were analysed after 96 hours. Mucosal T-cells and non-mucosal T-cells from paediatric controls (n = 15) and PIBD patients with active disease (n = 20) or disease in remission (n = 32) were analysed by flow cytometry.

Results

In healthy individuals, mRNA expression profiles of mucosal T-cells were enriched in genes associated with regulation and proliferation compared with non-mucosal T-cells of the same individuals. In particular, known regulatory molecules such as interleukin-10 and T-cell immunoglobulin and ITIM domain receptor (TIGIT) were increased. In a MLR, mucosal T-cells proliferated more extensively and a higher percentage of cells expressed forkhead box P3 and TIGIT compared with non-mucosal T-cells, albeit with variable results. To assess whether an altered activational state of circulating mucosal T-cells was detectable during active intestinal disease mucosal T-cell responses were monitored in PIBD. The median percentage of circulating mucosal T-cells did not differ between paediatric controls and PIBD patients. However, the frequency of naïve CD45RA+ T-cells was reduced in the mucosal T-cell population of patients with active disease when compared with mucosal T-cells of patients in remission or healthy controls. Consistent with persistent T-cell activation, increased frequencies of mucosal T-cells expressing the activation marker CD25 were detected in active disease when compared with patients in remission or healthy controls.

Conclusion

In a subpopulation of PIBD patients circulating mucosal T-cells have an activated phenotype when compared with mucosal T-cells in patients in remission or healthy controls.