IHC
As described by the source labs, specimens containing normal tissue were
collected and sampled from anonymized paraffin embedded material of
surgical specimens, in accordance with approval from the local ethics
committee. The specimens were derived from surgically removed tissue,
normal was defined by tissue specific morphological parameters and
absence of neoplasia. IHC staining was performed on normal tissue
microarray using a standard protocol
(https://www.proteinatlas.org/download/IHC_protocol.pdf). Antibodies
against human ACE2 (HPA000288, CAB026174), TMPRSS2 (HPA035787), CTSL
(CAB000459), and FURIN (CAB009499) were labeled with DAB (3,
3’-diaminobenzidine) stain. Protein expression score was calculated for
each receptor based on the staining intensity (negative, weak, moderate
or strong) and fraction of stained cells (<25%, 25-75% or
>75%). For each protein, the IHC staining profile was
matched with mRNA expression data and gene/protein characterization data
to yield an ‘annotated protein expression’ profile.