We found that club cells (formerly known as Clara cells), were consistently among the highest-expressing respiratory cell types (Figure 3A–B). Literature-derived local and global scores suggest that this ACE2-club cell connection is underappreciated. We also found that ACE2 is detected in type II pneumocytes in multiple studies, although the percentage of expressing cells ranges from only 0.5–7% (Figure 3A–B). This relatively low expression, which may be deemed inconsequential if viewed in isolation, is strongly supported by knowledge synthesis that highlights an existing association between ACE2 and type II pneumocytes (Figure 3A–B). Indeed, multiple studies have demonstrated ACE2 expression in these cells (Glowacka et al., 2011; van den Brand et al., 2008; Glowacka et al., 2010; Bertram et al., 2011; Hamming et al., 2004; Mossel et al., 2008; To and Lo, 2004). Further, ACE2 expression in bulk-RNAseq of GTEx lung samples (n = 578) is strongly correlated to markers of type II pneumocytes, with all seven surfactant protein-encoding genes among the top 4% of transcriptional correlations to ACE2 (out of the ~19,000 genes expressed at >1 Transcripts Per Million (TPM) in GTEx lung samples; hypergeometric p-value=1.1×10−10) (Figure 3—figure supplement 1).