CD4 and inflammatory bowel disease: In alignment with this, transcriptomic profiling of circulating CD4 T-cells has demonstrated marked molecular differences across the IBD spectrum.10 In a recent multiomics study of 163 patients with IBD, differences in the patterns of ileal and colonic inflammation were described based on analyses of the fecal metabolome, metaproteome, and microbiota composition.12 Our work complements these findings by examining serum protein profiles as an additional informative layer for defining the intricate landscape of IBD and identifying colonic CD as an intermediate between ileal CD and UC.