Furthermore, the complement proteins required for full functional activity can be collectively synthesised by various non-immune cells resident in the lung (alveolar type II epithelial cells55–57, AT2 cells57, club cells57, fibroblasts55,57, goblet cells57, mesothelial cells57, and mucous cells57) as well as immune cells capable of residing in the lung or migrating during infection (monocytes, macrophages, dendritic cells)58. Here, VTN is linked to infection.