Immune cell migration through the arterial wall in the murine lung during a pulmonary inflammatory response

Perivascular accumulation of leukocytes in the lung was induced by intratracheal administration of sheep erythrocyte antigen to primed mice. The route of migration of intravascular leukocytes to the perivascular space in the lung, in particular from arteries, and the structure of lymphatic vessels among the aggregated leukocytes were examined by transmission electron microscopy. Leukocytes--lymphocytes, granulocytes, monocytes and macrophages--were demonstrated to adhere to the endothelial surface and to migrate between endothelial cells to reach the internal elastic lamina of arteries. Becoming conspicuously constricted, the leukocytes penetrate through this elastic lamina. They further migrate through the smooth muscle layer to the interstitium, passing through the external elastic laminar region. At 2 days after antigen administration, dilated lymphatic vessels containing large numbers of leukocytes in the lumen and bearing endothelial gaps open to the interstitium began to be seen. The lymphatic walls were more convoluted and richer in pinocytotic vesicles than those prior to antigen challenge. This study confirms the light microscopic findings by Curtis et al. (1990) that arteries, besides veins, venules and capillaries, may represent a major route of inflammatory cell entry into the lung parenchyme in an acute and vigorous immune response. In addition, lymphatic vessels were suggested to be newly formed for the transport of fluid and immune cells from the sites of inflammation in the lung.