Angiocentric recruitment of lymphocytes into the lung after the intrabronchial instillation of antigen

The pathogenesis of acute lymphocytic inflammation in the lower respiratory tract appears to involve the recruitment of lymphocytes out of the blood stream and into the extravascular lung tissue. To investigate the membrane molecules regulating this process, we used the intrabronchial instillation of cellular antigen to trigger lymphocyte recruitment into the lower respiratory tract. Sheep presensitized 6 to 10 weeks earlier at a remote site were intrabronchially challenged with 1-5 x 10⁷ cells from a B lymphoblastoid cell line. The cells were instilled into a subsegmental bronchus through a bronchial catheter. The stimulated and contralateral control segments were studied at a peak of inflammation, approximately 72 hours after antigen stimulation. Gross and microscopic studies of the stimulated segment demonstrated localized inflammation characterized by the perivascular infiltration of lymphocytes. In contrast, control areas of the lung demonstrated only scattered perivascular lymphocytes. Immunohistochemistry of the stimulated lung showed that the majority of these perivascular cells were CD3⁺ CD4⁺ lymphocytes. The T lymphocytes expressed high levels of the cell adhesion molecules β1 integrin and LFA-1, but low levels of the L-selectin membrane molecule. Immunohistochemistry of the endothelial cells associated with the lymphocyte infiltrates demonstrated intense staining of the ICAM-1, and β1 integrin adhesion molecules. Electron microscopic studies of the endothelial cells in the antigen stimulated areas of the lung confirmed morphologic changes consistent with endothelialitis. These results suggest that the intrabronchial instillation of cellular antigen stimulates an angiocentric T-cell infiltration regulated by activated pulmonary endothelial cells. The histologic and morphologic findings are remarkably similar to those observed during acute lung transplant rejection.