In nonhuman primates, Vγ9Vδ2+ (Vδ2)T cells proliferate and accumulate in mucosal tissues following microbial activation. Human Vδ2T cells produce proinflammatory cytokines in response to bacterial species that colonize the gut, but the role played by Vδ2T cells in intestinal immunity is unknown. We hypothesized that circulating Vδ2T cells can populate the human intestine and contribute to mucosal inflammation. Cell suspensions prepared from peripheral blood and intestinal biopsies were stimulated with microbial phosphoantigen (1-hydroxy-2-methyl-2-buten-4-yl 4-diphosphate [HDMAPP]) and analyzed by flow cytometry to determine Vδ2T cell phenotype, cytokine production, and proliferative potential. Circulating Vδ2T cells expressed gut-homing integrin α4β7 (>70%), which was coexpressed with skin-associated cutaneous leukocyte Ag by up to 15% of the total population. However, Vδ2T cell activation with HDMAPP and exposure to retinoic acid (signaling via retinoic acid receptor α) increased α4β7 expression and enhanced binding to mucosal addressin cell adhesion molecule-1 in vitro while simultaneously suppressing cutaneous leukocyte Ag, thereby generating a committed gut-tropic phenotype. Confocal microscopy and flow cytometry identified frequent Vδ2T cells that migrated out of human intestinal biopsies and comprised both CD103+ and CD103− subsets that produced TNF-α and IFN-γ upon phosphoantigen exposure, with more frequent cytokine-producing cells in the CD103− population. Activated intestinal Vδ2T cells expressed CD70 and HLA-DR but were unable to drive the proliferation of allogeneic naive CD4+ T cells. Instead, phosphoantigen-activated CD103− Vδ2T cells increased T-bet expression and enhanced IFN-γ production by autologous colonic αβ T cells via an IFN-γ–dependent mechanism. These data demonstrate that circulating Vδ2T cells display enhanced gut-homing potential upon microbial activation and populate the human intestinal mucosa, generating functionally distinct CD103+ and CD103− subsets that can promote inflammation by colonic αβ T cells.

Mini AbstractPatients undergoing major surgery are at risk of life-threatening complications including systemic inflammatory response syndrome (SIRS) and sepsis. Early post-operative expression of TLR4 and TLR5 and their downstream signalling pathways in monocytes leads to over-expression of IL-6 and can predict SIRS in patients undergoing hepatopancreaticobiliary surgery. Running Title -Monocyte dysfunction in post-operative SIRS AbstractObjective To study innate immune pathways in hepatopancreaticobiliary (HPB) surgical patients to understand mechanisms leading to enhanced inflammatory responses and identifying biomarkers of adverse clinical consequences. Summary Background Data Patients undergoing major abdominal surgery are at risk of life-threatening systemic inflammatory response syndrome (SIRS) and sepsis. Early identification of at-risk patients would allow tailored post-operative care and improve survival. Methods Two separate cohorts of patients undergoing major HPB surgery were studied (combined n=69). Bloods were taken pre-operatively, on day 1 and day 2 post-operatively. Peripheral blood mononuclear cells and serum were separated and immune phenotype and function assessed ex vivo. Results Early innate immune dysfunction was evident in 12 patients who subsequently developed SIRS (post-operative day 6) compared to 27 who did not, when no clinical evidence of SIRS was apparent (pre-operatively or days 1 and 2). Serum interleukin (IL)-6 concentration and monocyte TLR/NF-DB/IL-6 functional pathways were significantly upregulated and overactive in patients who developed SIRS (p<0.0001). Interferon alpha-mediated STAT1 phosphorylation was higher pre-operatively in patients who developed SIRS. Increased TLR4 and TLR5 gene expression in whole blood was demonstrated in a separate validation cohort of 30 patients undergoing similar surgery. Expression of TLR4/5 on monocytes, particularly intermediate CD14 ++ CD16 + monocytes, on day 1 or 2 predicted SIRS with accuracy 0.89-1.0 (areas under receiver operator curves). Conclusions These data demonstrate the mechanism for IL-6 overproduction in patients who develop post-operative SIRS and identify markers that predict patients at risk of SIRS 5 days before onset of 30 patients undergoing similar surgery. Expression of TLR4/5 on monocytes, particularly intermediate CD14 ++ CD16 + monocytes, on day 1 or 2 predicted SIRS with accuracy 0.89-1.0 (areas under receiver operator curves).