Ultrastructural damage of leukocytes procured by the Leukopak: vulnerability of leukocytes to mechanical injury.

Because of the often observed undesired effects in patients transfused with leukocytes collected by continuous filtration leukapheresis (CFL), we have investigated the morphology of these cells in the hope that such studies may help evaluate their in vivo functions. Aliquots of CFL samples, procured by the Fenwal Leukopak and taken before and after tapping the filters, were examined. Leukocytes prepared by dextran sedimentation served as controls and were used to demonstrate the vulnerability of these cells to mechanical injury. The morphology of leukocytes harvested by filtration leukapheresis was markedly altered, ranging from formation of cytoplasmic projections and vacuoles to disintegration of entire cells. The severe changes were only observed in samples collected after the filters were tapped. The number of cells involved varied from donor to donor. In some cases more than half of the examined leukocytes showed signs of damage. Dextran sedimentation leukocytes retained their normal ultrastructure. However, substantial injuries were inflicted on dextran sedimentation collected leukocytes following brief periods of vortexing. Our results indicate that leukocytes are quite vulnerable to mechanical injury, and the major cause of damage found in Leukopak-isolated leukocytes is the tapping of the filters. The toxic reactions in some recipients transfused with Leukopak-collected leukocyte preparations may result from materials released from disrupted leukocytes. We believe that the employment of the continuous filtration to procure leukocytes with the present procedure should be reviewed.