IL-22 belongs to the IL-10 cytokine family (Zenewicz and Flavell, 2011) and is produced in the intestinal mucosa by group 3 innate lymphoid cells (ILC3s; produces IL-22 during the early stage of infection) and CD4 + T cells (including Th17 cells and Th22 cells; produces IL-22 during late stage of infection) (Ngo et al., 2018). The gene discussed is CD4; the disease is infection.