Figure 2. Activation marker expression by T cells in COVID-19 patients.(A) Expression of HLA-DR+(%) in CD4 (left panel) and CD8 (right panel) cells in children and adults with COVID-19 as compared to respective control subjects and analyzed by flow cytometry. Data are shown as median±semi-interquartile range (% of cells). HLA-DR expression was measured on a single blood sample collected at the time of hospital admission. Kruskal–Wallis comparison test was used to compare between healthy control subjects, COVID-19 children, and adults values of CD4+/HLA-DR+ cells (p< 0.0001) and of CD8+/HLA-DR+ cells (p< 0.0001). When the test was statistically significant between three groups, Dunn’s multiple comparison test was used for pairwise differences of CD4+/HLA-DR+ and CD8+/HLADR+ cells between control group and COVID-19 children or adults. This analysis showed a significant difference in the values of CD4+/HLA-DR+ and of CD8+/HLA-DR+ in COVID-19 adults as compared to control subjects (p< 0.005).(B) Cytokines evaluation in children and adults affected by COVID-19. Plasmatic levels of IL-1beta, IL-12 (p70) in 14 children and 10 adults with COVID-19 were measured by Bead Array flow cytometry assay on a single plasma sample at the time of hospital admission. Data are shown as mean±standard deviation (pg/mL). Mann–Whitney comparison test showed significant differences of IL-1β and IL-12 values between COVID-19 children and adults (p< 0.05).