FIGURE 11.

Scheme for Csf1-dependent myeloid cell inputs to ILC2 function in chronic disease after respiratory viral infection. Sequential steps in the scheme include: (1) acute illness with damage to host cells, including progenitor AT2 cells and daughter alveolar epithelial type 1 (AT1) cells; (2) subsequent replacement of these populations including AT2 cells that provide increased IL-33 to activate ILC2 production of IL-13 and in turn IL-13R-dependent differentiation of epithelial stem cells into mucous cells. The Csf1-dependent myeloid cells act upstream for induction of Il33 gene expression and downstream to provide tissue macrophages for additional Il13 gene expression that is required for full development of chronic lung disease after viral infection.