Increased lymphangiogenesis in LTβ^−/− mouse tracheas after infection with Mycoplasma pulmonis. (A) LYVE-1⁺ lymphatic vessels (red) and (B) CD31⁺ blood vessels (green) increase in the tracheas of mice infected with M pulmonis. Scale bar is 200 μm (Zeiss 510 Confocal Microscope). (C) Quantification reveals a significant increase in lymphatic vessel density in the tracheas of LTβ^−/− mice compared with both LTα^−/− and WT mice (*P < .05). (D) A similar increase was noted in blood vessel density.