(a) UMAP projection of canonical markers for different cell types as indicated (n = 13). (b) A heatmap showing expression of hallmark genes by different cell clusters. The makers and their corresponding cell clusters are listed on the right side. (c) The alignment of BALF cell clusters by UMAP across control (n = 4), moderate (n = 3) and severe/critical (n = 6) COVID-19 cases. (d) The UMAP plots of each studied subject, including 4 controls (HC1 to HC4), 3 moderate cases (M1 to M3), and 6 severe / critical cases (S1 to S6). (e) The bar plot shows the relative contributions of each cluster by each studied subject. (f) The table shows the percentages of various immune cell populations in the BALFs among different groups of studied subjects. HC1-HC4: healthy controls, M1-M3: moderate cases, S1-S6: severe/critical cases.