RAG2 and colitis: In contrast, Gr1+ cells, representing infiltrating Ly6Chi Gr1int monocytes and Ly6Cint Gr1hi neutrophils, were readily detected in Trem1+/+ x Rag2+/+ mice and Trem1−/− x Rag2−/− mice at 12–13 days post colitis induction (Fig. 4A).