Materials and Methods
We performed in silico analysis of mRNA and protein expressions of ACE2, TMPRSS2, CTSL, and FURIN in human immune system components (bone marrow, bone marrow, and lymphoid tissue—thymus, appendix, spleen, lymph nodes, spleen, tonsil) using tissue transcriptome and immunohistochemistry (IHC) data available in Human Protein Atlas (HPA) (https://www.proteinatlas.org/). Further, mRNA expression across blood cell types were analyzed using single cell RNA sequencing data available in ‘The Blood Atlas (a section of HPA)’.