FOLR2 and COVID-19: Among markers suggested above, five markers were selected for additional study: SLC2A3, FOLR2, CCR1, FPR1, and GPR183. In scRNA-seq data from GSE147143 dataset (BAL fluid of severe COVID-19 patients), SLC2A3, CCR1, and FPR1 were highly expressed in the macrophage and neutrophil clusters.