Furthermore, although monocytes showed the most notable drop in cell count when comparing critical to mild-moderate condition evaluated by CyTOF and scRNA-seq, the latter revealed a significant decrease in non-classical monocytes (based on C1AQ, C1BQ and LSTB1 marker expression) and a corresponding relative increase of classical monocytes (based on S100A8, S100A9 and S100A12 marker expression) in critical COVID-19 (Fig. 2a and Suppl. The gene discussed is S100A9; the disease is COVID-19.