Given that the primary goal of the current study was to characterize genetic factors that exert an effect on peripheral immune cell types for severe COVID-19, the majority of our subsequent detailed analyses would be concentrated on three immune cell subpopulations: CCR1+ CD16+monocytes, ABO+ megakaryocytes, and CXCR6+ memory CD8+T cells (Fig. 3B). Here, ABO is linked to COVID-19.