A tangential flow filtration device for preparing a cell population enriched for leukocytes by selectively removing blood constituents such as plasma, platelets and erythrocytes, comprising: a remover unit having a cylindrical cross-flow chamber and a filtrate chamber separated by a filter disposed therebetween, the filter in fluid communication with the cross-flow chamber and the filtrate chamber; the filter diameter is substantially the same as the diameter of the cross-flow chamber; the cylindrical cross-flow chamber having an inlet and an outlet, the inlet disposed adjacent to the retentate surface of the filter to introduce a sample of blood constituents comprising leukocytes into the cross-flow chamber and parallel to the retentate surface of the filter; and the outlet located adjacent to the center of and perpendicular to the retentate surface of the filter; the filtrate chamber having an outlet; a recovery unit comprising a housing, an inlet and an outlet, the cross-flow chamber and the recovery unit interconnected in a loop format, wherein the cross-flow chamber inlet is in fluid communication with the recovery unit outlet, and the cross-flow chamber outlet is in fluid communication with the recovery unit inlet; a pump to pump fluid into the cross-flow chamber through the inlet, and configured to introduce the fluid into the cylindrical cross-flow chamber at an input rate of 5 to 100 times the filtration rate; wherein this arrangement causes the flow of fluid in the cross-flow chamber to spiral inward toward the center of the filter creating a vortex motion with the fluid, the filter having an average pore size ranging from 3 to 8 microns such that flow of the sample across the filter enriches the sample of blood constituents for leukocytes, and the remover unit further comprises a pump controlling the removal of the filtrate from the filtrate chamber of the remover unit. a remover unit having a cylindrical cross-flow chamber and a filtrate chamber separated by a filter disposed therebetween, the filter in fluid communication with the cross-flow chamber and the filtrate chamber; the filter diameter is substantially the same as the diameter of the cross-flow chamber; the cylindrical cross-flow chamber having an inlet and an outlet, the inlet disposed adjacent to the retentate surface of the filter to introduce a sample of blood constituents comprising leukocytes into the cross-flow chamber and parallel to the retentate surface of the filter; and the outlet located adjacent to the center of and perpendicular to the retentate surface of the filter; the filtrate chamber having an outlet; a recovery unit comprising a housing, an inlet and an outlet, the cross-flow chamber and the recovery unit interconnected in a loop format, wherein the cross-flow chamber inlet is in fluid communication with the recovery unit outlet, and the cross-flow chamber outlet is in fluid communication with the recovery unit inlet; a pump to pump fluid into the cross-flow chamber through the inlet, and configured to introduce the fluid into the cylindrical cross-flow chamber at an input rate of 5 to 100 times the filtration rate; wherein this arrangement causes the flow of fluid in the cross-flow chamber to spiral inward toward the center of the filter creating a vortex motion with the fluid, the filter having an average pore size ranging from 3 to 8 microns such that flow of the sample across the filter enriches the sample of blood constituents for leukocytes, and the remover unit further comprises a pump controlling the removal of the filtrate from the filtrate chamber of the remover unit.