CA4 and swine influenza: At 14 days post H1N1 influenza injury, quantitative analysis of Car4+/Pecam+ double-positive cells in different zones of injury (Zacharias et al., 2018) demonstrated an increase in number of double-positive cells in regions of mild to moderate injury (zones 1/2) (Figure 3—figure supplement 2B,D) as well as in regions adjacent to severe alveolar damage (zone 3) (Figure 3—figure supplement 2C,D).