Immunohistochemical and immunofluorescent staining of allografts and colon biopsies were performed as previously described.21 (link) Cytokeratins, Ly6A/E and Dclk1 were stained using mouse anti-pancytokeratin monoclonal antibody (Novus Biologicals), rat anti-Ly6A/E (BD BioSciences) and rabbit polyclonal antibody to Dclk1 (Abcam). Rabbit anti-nitric oxide synthase 2 (Enzo Life Sciences), anti-arginase 1 (Sigma), and anti-MSH2 (Santa Cruz Biotechnology) polyclonal antibodies were used for Western blots.