TNF and inflammatory bowel disease: Colon length is a quantitative measure of disease severity where the extent of inflammation directly correlates to increased edema, leading to an overall shortening of the colon.29 In concert, elevation of pro-inflammatory cytokines also correlates with increased disease pathology in IBD.30 Although we observed enhanced colon length shrinkage in GrzM- and TCRδ-deficient mice after DSS-induced UC, in agreement with the weight loss data we only observed elevation of G-CSF and TNF in the serum of GrzM-deficient mice (Supplementary Figure 2F–H).