We addressed several potential confounding factors: First, we compared patients with PSC with IBD with those without IBD but could not find differences between the 2 patient groups concerning serum levels of cytokines, frequencies of proinflammatory CD4+ T cells in unstimulated PBMCs, and numbers of phospho-STAT3+ IFN gamma–producing and IL-17A–producing CD4+ T cells after in vitro stimulation of PBMCs with IL-6 (see Supplementary Figures 6A–6F, Supplementary Digital Content, http://links.lww.com/CTG/A950). This evidence concerns the gene CD4 and inflammatory bowel disease.