IL22 and pneumonia: Accordingly, compared with healthy control individuals, the IL-22+-Tc22 and IL-22+-Th22 numbers in adult-COVID-19 patients increased significantly, whether it is asymptomatic pneumonia, mild pneumonia, or severe pneumonia (Figure 4). These findings further suggest that in the 0-12-year-old age group with asymptomatic disease course and uncomplicated adult cases, IL-22 expressed Tc22 cells are higher, which indicates that IL-22 has a protective effect (89).