Lymphangiogenesis and angiogenesis after M. pulmonis infection. (A–C, E, and F) Confocal micrographs of tracheal whole mounts stained for lymphatic vessels (red) and blood vessels (green). (A) Pathogen-free C3H mouse. (B) C3H mouse infected for 14 days; inset shows lymphatic sprouts (arrowheads) and filopodia (arrows). (C) C3H mouse infected for 28 days. (D) Proliferation of lymphatic vessels (red) and blood vessels (green) in tracheas of C3H mice over 28 days of infection. (E) In a C57BL/6 mouse infected for 14 days, blood vessels (CD31) exhibit sprouting (arrow) and enlargement. (F) Same region as shown in E. Lymphatic vessels (LYVE-1) have a growth pattern similar to that of C3H mice. (G, H, J, and K) Dividing endothelial cells stained for phosphohistone H3 (PH3, green) in tracheal lymphatic vessels (red) of C3H mice infected for 14 days. (G) Section of trachea showing dividing cells, which are sparse in lymphatic vessels (arrow) and numerous in epithelial cells and leukocytes (asterisks). (H, J, and K) Tracheal whole mounts. (H) Dividing lymphatic endothelial cells (arrows) in stalks of medium-sized sprouts. (I) Size distribution of 100 dividing lymphatic endothelial cells. Most dividing cells are near sprout tips (J) or in larger lymphatic vessels (K). (L) Distribution of distances of dividing lymphatic endothelial cells from sprout tips. Scale bar in K applies to all figures: 100 μm in A–C, E and F, and 20 μm in G, H, J, and K.