γδ intraepithelial lymphocytes facilitate pathological epithelial cell shedding via CD103-mediated granzyme release.

Abstract

Excessive shedding of enterocytes into the intestinal lumen is observed in inflammatory bowel disease and is correlated with disease relapse. However, the mechanisms underlying this phenomenon remain unclear. Intraepithelial lymphocytes (IEL) expressing the {gamma}{delta} T-cell receptor (TCR) provide surveillance of the intestinal mucosa at steady-state, which is regulated, in part, by CD103. Intravital microscopy of lipopolysaccharide (LPS)-treated mice revealed that {gamma}{delta} IELs make extended contact with shedding enterocytes. These prolonged interactions require CD103 engagement by E-cadherin, as CD103 blockade significantly reduces LPS-induced shedding. Furthermore, we find that granzymes A and B, but not perforin, are required for cell shedding, and that these granzymes are released by {gamma}{delta} IELs both constitutively and following CD103/E-cadherin ligation. These findings indicate that extracellular granzyme facilitates shedding, likely through cleavage of extracellular matrix proteins. Our results uncover a previously unrecognized role for {gamma}{delta} IELs in facilitating pathological cell shedding in a CD103- and granzyme-dependent manner.