MPO and colitis: Fecal transplantation induced colitis in young mice, as indicated by colon shortening and an increase in myeloperoxidase activity, NF-κB activation, p16 and IL-1β expression, and NF-κB+/CD11c+ cell counts in the colon (Fig. 1H –M, Supplement Figure S2I–K, Supplement Figure S3E, F).