P092 Characterisation of the lymphoid stress surveillance response performed by human colon resident γδ T-cells
R. J. Dart*1, 2, 3, R. Woolf2, P. M. Irving3, A. C. Hayday1, 2
1Francis Crick Institute, Immunosurveillance Lab, London, United Kingdom, 2King’s College London, Immunobiology, DIIID, London, United Kingdom, 3Guy’s and St Thomas’ NHS Foundation Trust, IBD Centre, London, United Kingdom
The human intestine harbours an immense repertoire of T-cells; this includes unconventional T-cells, such as intestine-resident γδ T-cells, which have proved difficult to isolate, leaving their function and significance enigmatic. The lymphoid stress surveillance response (LSSR), whereby unconventional T-cells respond to epithelial dysregulation in synchrony with innate myeloid cells, was first described in mice. Stress ligands implicated in the LSSR are upregulated in inflammatory bowel disease; thus, it is imperative that we understand the potential response to them of human intestine-resident γδ T-cells, with potential to affect gut inflammation.
Using colonic biopsies obtained at endoscopy from healthy donors, we have applied a novel explant culture system (based on 1 described for human skin), permitting outgrowth of large numbers of viable T-cells, suited to phenotyping and functional characterisation.
To validate our method, we performed critical comparisons between T-cell isolation methods, demonstrating a 2-fold increased cell yield compared with conventionally isolated cells. We could conclude that γδ T-cells comprise a significant, underappreciated proportion of total intestinal lymphocytes (9.5% ± 9). Gut γδ T-cells express a tissue-resident memory phenotype, including the activating receptor NKG2D, and have overt capacity to respond to IL12 and IL18 in the absence of specific TCR stimulation. In the presence of specific cytokines, such as IL-15, these cells are also licensed to make cytotoxic responses and produce TNFα in response to recombinant NKG2D ligands alone. Moreover, cytotoxic responses to colonic tumour cell lines were abrogated by antibodies that block NKG2D.
The human intestine harbours a large number of tissue-resident γδ T-cells that can make rapid, innate-like responses to epithelial cell dysregulation, akin to those shown in vivo for their mouse counterparts, and akin to responses that our lab has shown for human skin. This provides a platform to identify important contributions that γδ T-cells make via the LSSR inflammatory bowel disease, which is characterised by tissue dysregulation and the up regulation of stress ligands. By understanding the role of colonic γδ T-cells in this context we can open up new potential therapeutic avenues and utilise previously developed drugs in the treatment of inflammatory bowel disease.