ANXA5 and infection: Quantification of phosphatidylserine externalization by Annexin V expression of non-infected and PR/8 infected wt mice at d7 pi, a time point where apoptotic epithelial injury is most prominent in the lungs [8, 28], revealed that EpiSPC were resistant to IV-induced apoptosis, whereas the other EpCam+ populations showed high levels of apoptosis in response to infection (Fig 2B).