Figure 8.

Schematic diagram of prevention and reversibility of blood vessel and lymphatic remodeling in M. pulmonis-infected airways. Blood vessels are shown in green, lymphatics in red, and leukocytes in blue in three conditions: infected and untreated (A); dexamethasone-prevention studies (B); and dexamethasone-reversal studies (C). In pathogen-free airways, vessels show normal baseline appearance with little or no leukocyte influx. A: In infected and untreated airways, uniform, thin capillaries enlarge into venules that support leukocyte recruitment, followed later by angiogenic sprouting. Leukocyte influx increases as infection continues. The normal lymphatic vessel network expands first by sprouting and then by enlargement and growth and fusion of newly formed lymphatics. B: In prevention studies, when dexamethasone is given concurrently with infection, blood vessels and lymphatics do not undergo extensive remodeling but remain similar to the pathogen-free state with little or no leukocyte influx. C: In reversal studies, delayed dexamethasone treatment reverses enlargement of blood vessels and growth of angiogenic sprouts almost to pathogen-free values. Leukocyte influx is reduced, as the blood vessels are less remodeled. In contrast to blood vessels, newly formed lymphatics are much more resistant to reversal, except for the disappearance of fine filopodia and formation of some disconnected lymphatic islands.