Separation and purification of leukocytes and platelets.

quantities of blood and generally employ extensive mechanical equipment. The former have the advantage of low cost and simplicity, but usually yield leukocytes which are not as normal biologically as the leukocytes separated with more complex, refrigerated equipment. All methods (except one)* utilize the difference in density of the three formed elements : red cells 1 .092, leukocytes 1 .065, platelets 1 .030. Gravitational force is employed either at 1 G, as in sedimentation, or at x G as in mechanical ceistrifuges. Efforts to utilize characteristics other than density have met with limited or no success: i.e., utilization of surface charge by migration in an electrophoretic cell; phagocytosis of iron particles followed by exposure to a magnetic field; specific antisera (antiplatelet antibodies, antileukocyte antibodies); and specific cell toxins such as saponin to lyse erythrocytes. All these methods are predicated on purification of a single formed element through destructiots of the other formed elements and thus are manifestly wasteful of blood. The constaistly increasimsg use of blood and blood derivatives demands economy and specificity its the utilization of its component parts.