CD19 and infection: During SARS-CoV-2 infection progress, CD3 cells, CD19 cells, natural killer (NK) cells and macrophages in PBMC of mice were suppressed; on the other hand, regulatory T (TREG) cells, Th1 cells, Th2 cells and Th17 cells could be stimulated in the infection process but maintained high levels for only a short time (Figure 2(a–d)).