Identification of mucosal-associated invariant T cells in pancreatic tissue and blood of patients with chronic pancreatitis. (13th March 2011) - Jupp, J
Abstract : Introduction: Mucosal-Associated Invariant T cells (MAIT) are recently described human T lymphocytes with possible functions in mucosal antibacterial host defence.1 MAIT express a highly conserved T cell receptor (TCR) alpha chain consisting of an invariant Vα7.2-Jα33 rearrangement.2 Recent evidence suggests a role for T lymphocytes in the pathogenesis of chronic pancreatitis (CP), but little is known about the composition of T cell subsets in this disease.3 4 Intestinal bacterial overgrowth is common in chronic pancreatitis patients.5 We hypothesised that this antigenic load may promote MAIT infiltration of the pancreas and used flow cytometry to study T lymphocytes in resected pancreatic tissue and blood of patients with chronic pancreatitis. Methods: Fresh resected pancreatic tissue from five patients with CP (5 males, aged 35–62, median age 43) was diced finely, enzymatically digested and passed through a nylon mesh. Lymphocytes were then isolated using density gradient centrifugation. Peripheral blood mononuclear cells (PBMCs) were isolated from the blood of the CP patients and four control patients (2 male, 2 female, aged 31–75, median age 41) using widely established techniques. Isolated tissue lymphocytes and PBMCs were analysed with fluorochrome conjugated antibodies (anti- CD3; CD4; CD8; CD161; TCR Vα7.22 and a live/dead stain) according to standard techniques using a FACSAria. Results: The ratio of CD4:CD8 T cells found in pancreatic tissue compared to blood in patients with CP trended towards a higher ratio in blood, however the trend was not statistically significant. Double negative (DN) and CD8 MAIT cells (TCR Vα7.2+ CD161) were identified in pancreatic tissue and blood in all patients. The proportion of DN MAIT cells was significantly higher in pancreatic tissue compared to blood in patients with CP: 19.4% (5.7–39.6%) versus 5.2% (1.9–11.1%); p<0.05. The proportion and ratio of CD4 and CD8 T cells was similar in peripheral blood of patients with CP compared to controls. Conclusion: These preliminary data show that while the distribution of CD4 and CD8 lymphocytes in CP tissue and blood is similar, DN MAIT cells are over-represented in tissue. This suggests a specific role for DN MAIT cells in local immune responses in CP. Further analysis using a larger patient cohort and functional studies to assess the possible role of these cells in the regulation of pancreatic inflammation are required.