MECHANICAL TRAUMA IN LEUKOCYTES

Abstract

Mechanical and surface traumas in cardiopulmonary bypass circuits alter the function and morphology of human leukocytes. The effect of controlled in vitro shear stress (0-2000 dyn/cm2, 2-10 min, 37.degree. C) on electronic cell count, morphology, adhesiveness and phosphatase cytochemical staining was studied on whole blood from normal donors. Electronic cell counts dropped significantly after shear stress exposure (25% at 600 dyn/cm2 for 10 min). The frequency of disrupted leukocytes in blood smears increased with shear stress above 150 dyn/cm2, and aggregates of the disrupted cells appeared after exposure to higher shear stresses (450 dyn/cm2, 10 min). Cytochemical staining of the alkaline phosphatase in the granules of intact neutrophils was significantly reduced by the application of shear stress (150 dyn/cm2 for 10 min or greater), but staining of acid phosphatase-containing granules was almost unaffected. Increased cell retention in columns of nylon fibers suggests that increased leukocyte adhesiveness results from exposure to shear stress. Exposure to shear stress may alter or disrupt leukocyte morphology and function at values somewhat lower than the 1500 dyn/cm2 for 2 min which is required to hemolyze erythrocytes.