LAUSR

BACKGROUND & AIMS Excessive shedding of apoptotic enterocytes into the intestinal lumen is observed in inflammatory bowel disease and is correlated with disease relapse. Based on their cytolytic capacity and surveillance behavior, we investigated whether intraepithelial lymphocytes expressing the γδ T cell receptor (γδ IELs) are actively involved in the shedding of enterocytes into the lumen. METHODS Intravital microscopy was performed on GFP γδ T cell reporter mice treated with intraperitoneal (i.p.) lipopolysaccharide (LPS, 10 mg/kg) for 90 min to induce tumor necrosis factor (TNF)-mediated apoptosis. Cell shedding in various knockout or transgenic mice in the presence or absence of blocking antibody was quantified by immunostaining for ZO-1 funnels and cleaved caspase-3 (CC3). GzmA and GzmB release from ex vivo stimulated γδ IELs was quantified by ELISA. Immunostaining for γδ T cell receptor (TCR) and CC3 was performed on duodenal and ileal biopsies from control and Crohn's disease patients. RESULTS Intravital microscopy of LPS-treated mice revealed that γδ IELs make extended contact with shedding enterocytes. These prolonged interactions require CD103 engagement by E-cadherin, and CD103 knockout or blockade significantly reduced LPS-induced shedding. Furthermore, we find that granzymes A and B, but not perforin, are required for cell shedding. These extracellular granzymes are released by γδ IELs both constitutively and following CD103/E-cadherin ligation. Moreover, we find that the frequency of γδ IEL localization to CC3-positive enterocytes is increased in Crohn's disease biopsies compared to healthy controls. CONCLUSION Our results uncover a previously unrecognized role for γδ IELs in facilitating TNF-mediated shedding of apoptotic enterocytes via CD103-mediated extracellular granzyme release.