Similar to the proSP-C data, mSP-B was expressed in the majority of the bona fide AEC2s (Q2: HTII-280pos mSP-Bpos) in both donor and IPF, and their proportion was drastically reduced in IPF (Figure 3E,F and Supplemental Figure S3D). The gene discussed is PROS2P; the disease is idiopathic pulmonary fibrosis.