Evaluation of Integrin aE-positive and negative cells

Etrolizumab, a humanized monoclonal antibody that selectively binds the b7 subunit of the heterodimeric integrins a4b7 and aEb7, is currently in development for patients with moderate-to-severely active UC. Integrin aE forms a heterodimer with b7; and aEb7 interacts with E-cadherin to mediate retention of aEb7+ cells in the intestinal epithelium. Baseline integrin aE levels have been identified as a potential predictive biomarker for etrolizumab response. Additional markers, including granzyme A, have also been identified and are being developed in partnership with Roche Molecular as potential predictive biomarkers for etrolizumab along with integrin aE. Extensive work has been done to characterize gut aE+ T cells by immunohistochemistry, flow cytometry and qPCR. We hope to use this project to validate differences between aE+ and aE- cell populations using CD4, CD8 and granzyme A expression as controls. The results from this project will be used to pilot single cell sequencing of CD3+aE+ cells isolated from the gut mucosa to identify cellular heterogeneity within aE+ cells under normal and inflammatory conditions. Materials and methods: Mucosal lymphocytes were isolated using a collagenase digestion from surgical specimens taken during routine gastrointestinal resections of diverticulitis and ulcerative colitis patients. CD45+TCRab+TCRgd- cells were sorted into aE+ and aE- groups. RNA was isolated from CD45+TCRab+TCRgd- T cells sorted into aE+ and aE- subsets. **Raw data not provided for patient privacy reasons** Raw data not provided due to patient privacy concerns