CTSD and COVID-19: The genes downregulated in the CAM monocytes, compared to the monocytes from the COVID-19 patients, include those for the mannose receptor (MRC2), lysosomal cathepsins (CTSB, CTSD, CTSL, CTSZ), legumain (LGMN), and lysosomal acid lipase A (LIPA), which were observed to be rather upregulated in the COVID-19 patients, compared to the healthy monocytes (Fig. 2C).