SEQUESTRATION OF LEUKOCYTES BY THE ISOLATED PERFUSED RAT LUNG

The sequestration of rat leukocytes and bone marrow cells by the lung vasculature was studied using an isolated perfused rat lung preparation. The passage of latex particles of 7.6 µm in diameter and non-hematopoietic cells through the lung blood vessels was also studied. Leukocytes and bone marrow cells were reversibly sequestered from circulation, whereas, latex particles and non-hematopoietic cells were removed irreversibly. Continuous circulation of leukocytes or bone marrow cells results in a steady state at which circulating cells and the lung reach some kind of equilibrium wi th no net cell removal by the lung. Further cell removal or release can occur by changing the circulating cell concentration. Removal of Ca++ and Mg++ from circulating medium decreased the sequestration of leukocytes by the lung. Complement activation is not involved in this process, since whole blood as well as serum free suspension of leukocytes, bone marrow cells or peritoneal cavity neutrophils showed similar patterns of sequestration. The results indicate that cell sequestration by the isolated perfused lung is a physiological process which can be considered as a suitable model of the in-vivo sequestration of blood leukocytes by the vascular system of the body. The pattern and the rate of sequestration depends on the cell type, cell concentration in circulation, and chemical factors in circulating medium. The results provide new information about the mechanisms which might be responsible for the sequestration of leukocytes by the lung vasculature in the absence of complement activation