RAG1 and colitis: To do so, we isolated DAPI−CD45+CD3+CD4+CD8− cells from the ceca of adoptively transferred Rag1−/−mice with colitis (Day 21) and from control adoptively transferred Rag1−/− mice without disease (Day 21), cocultured them with C57BL/6 mouse primary IECs (Cell Biologics, Chicago, IL) and examined cell survival using a CellTiter-Glo Luminescent Cell Viability Assay Kit (Fig. 4A).