BRIEF REVIEWS Interactions of Granulocytes with the Lungs

ALMOST seventeen billion granulocytes enter and exit the lungs each minute. Although the numbers of granulocytes in pulmonary artery and systemic artery blood are equal under normal conditions, they are not all the same cells, since a sizeable marginated pool of granulocytes in the lungs is constantly exchanging with the pool of circulating cells (Bierman et al., 1952, 1955; Cohen et al., 1979; Staub et al., 1981; Cohen et al., 1982). Some relatively innocuous interventions (for example, hemodialysis) cause sudden, dramatic stasis of granulocytes in the pulmonary circulation—granulocytes virtually disappear from the blood briefly—without severely compromising lung function (Craddock et al., 1977). In other circumstances, activated granulocytes sequestered in the lung appear to cause severe injury which may be either acute or chronic (Heflin and Brigham, 1981; Loyd et al., 1983; Newman et al., 1983). There is even some evidence that normal functions of the lungs may be influenced by granulocytes (Hinson et al., 1982).