It is difficult to infer exact mucosal concentrations due to the spatially restricted expression of IL-22; however, it seems likely that measurable elevation of serum concentrations in active IBD (in the range of up to 0.5 ng/ml; Nikolaus et al., 2017), as well as in vitro secretion capacity from biopsies from experimental models of intestinal inflammation (Bachmann et al., 2010), reflect local IL-22 levels, which may well reach the range of the concentrations (1–100 ng/ml) used in the present study. The gene discussed is IL22; the disease is inflammatory bowel disease.