PSMB9 and COVID-19: Specifically, along with CD68 (Fig. 3D), the immunoproteasome-related genes PSMB8 (Fig. 3E), TAP1, PSMB9, PSMB10, and calreticulin (CALR) (Additional file 1: Figure S1) were all found to be expressed in the CD14+/CD16+ subpopulation of cells during mild COVID-19 (Fig. 3A).