A leukopak is an enriched apheresis product containing a concentrated collection of leukocytes. Along with this high concentration of leukocytes, there are residual red blood cells and platelets not separated during leukapheresis. Leukopaks also contain a high concentration of peripheral blood mononuclear cells, or PBMCs. Fresh leukopaks require immediate washing, whereas frozen or cryopreserved leukopaks can last months until use, which is optimal for large-scale research with leukopaks.
Leukopak Cell Washing Protocol
Cell washing begins with the addition of a buffer solution like phosphate-buffered saline with fetal bovine serum to dilute the cell solution. After dilution, the sample is spun in a counterflow centrifuge, causing the cells to pellet at the bottom of the tube. The supernatant above the pellet is removed carefully, to not disturb the pellet of fragile cells, and the pellet is resuspended in any preferred fresh buffer solution. This process can be repeated several times to minimize unwanted contaminants.