PBX1 and COVID-19: Regarding the MkP-priming TFs, significant co-expression of ETS2-FLI1-GATA2-PBX1 and SPI1-LMO4 was observed in the HSC/MPPs from COVID-19 patients (Fig. 4a), with 75.8% and 61.4% of HSC/MPPs co-expressing ETS2 and FLI1 in the mild and severe cases, respectively, compared with 8.4% in HC (Fig. 4b).