Intra-vital Observation of Lung Water Retention Following Intravenous Injection of Anti-MHC-class I (H-2K) Monoclonal Antibody in Mice

Leukocyte activation is thought to be a major step in sepsis-induced pulmonary edema. We attempted to confirm whether pulmonary edema can be reproduced under intravital microscopy in a model of transfusion-related acute lung injury (TRALI) using MHC class I-specific antibody. The surface pulmonary microcirculation was observed using an epi-fluorescence microscope through a thoracic window in 50 male mice. Monoclonal MHC class I-specific antibody (Ab) was administered to the animals, while the control group received saline. The leukocytes and macro-molecular leakage in the pulmonary circulation were analyzed. Leukocytes accumulated in the capillaries (52.5±12.7 leukocytes per designated area in Ab group vs. 20.8±3.1 in control). The air-containing alveolus area significantly shrank from 2,224.9±934.9 μm to 509.7±380.8 μm in the Ab group. Pulmonary edema develops rapidly following leukocyte accumulation in the lung. We confirmed that leukocyte accumulation without an underlining condition is sufficient to induce pulmonary edema.