Aberrant intra-epithelial lymphocytes cause enterocyte cell death in refractory celiac disease by CD103-β7-receptor-mediated granzyme-B degranulation which can be restored by etrolizumab.

OBJECTIVES

Refractory celiac disease type II (RCDII) is an intestinal tumor of aberrant intra-epithelial T-lymphocytes (IEL). The severe enteropathy found in RCDII is caused by aberrant IEL that exert cytotoxicity against enterocytes. In this study, we investigated the cell death mechanism responsible for villous atrophy in RCDII.

METHODS

Aberrant IEL were isolated from duodenal biopsies of RCDII patients. Enterocyte and RCDII patient-derived cell lines and human small intestinal organoids were used. mRNA expression was determined with reverse transcriptase-multiplex ligation-dependent probe amplification. Protein expression, degranulation and enterocyte killing were measured using flow cytometry, immunofluorescence or bright field microscopy. Secretion of granzyme-B was detected by enzyme immunoassay.

RESULTS

Levels of granzyme-B expression were significantly upregulated in aberrant IEL of RCDII patients compared to patients with celiac disease (CD) on gluten-free diet (P = 0.0001) and correlated with severity of villous atrophy and clinical response to therapy. Killing of intestinal epithelial cells was caused by granzyme-B. For granzyme-B degranulation and subsequent cytotoxicity, cell-cell binding via the CD103-receptor, which was upregulated on aberrant IEL, was essential. In a preclinical model, aberrant IEL migrated to the intestinal organoids and induced organoid disintegration and CD103-dependent cell death. Targeting CD103-heterodimeric partner β7 with therapeutic monoclonal antibody etrolizumab prevented enterocyte cell killing and resulted in survival of organoids.

CONCLUSION

Killing of enterocytes in RCDII patients depends on degranulation of granzyme-B by aberrant IEL through CD103-β7 binding. By blocking this interaction, etrolizumab restores the intestinal epithelium and therefore should be considered as potential therapy for RCDII patients.