The preference of each cluster in different patient groups was illustrated: proliferative cells marked by MKI67 and plasma cells characterized by MZB1 were more enriched in severe COVID‐19 patients during the disease progression stage (highlighted with yellow and red lines, respectively), while CD8+ naïve T cells, expressing CD8A, LEF1, and TCF7, and Vd2‐ Vg9‐ gamma‐delta T cells (GDT), expressing KLRC2 and CMC1, were predominantly found in HC (highlighted with green lines) (Figure 1B,C and Supporting Information S2–S4: Figures 2, 3 and 4B). Here, KLRC2 is linked to COVID-19.