In patients with unstable remission, experiencing a future flare, multiple correlation analyses of significantly different serum markers in IBD T1-samples (Fig. 1C, Table 2) as well as routine blood and fecal markers of inflammation (Table 1; Supplementary Table S1) revealed that mainly markers which can be linked to T cell activation (IL-15, IL-18, IL-21, IL-25) or IFNγ-signaling (CXCL9) but also IL-1β and IFNβ cluster together in positive association (Fig. 2). Here, IL21 is linked to inflammatory bowel disease.