Disclosed is a method for purifying leukocytes, the method comprising (a) passing a biological fluid comprising leukocytes, or a cryoprotectant fluid comprising leukocytes, through a porous leukocyte depletion medium having an upstream surface and a downstream surface, the fluid passing from the upstream surface through the downstream surface, wherein leukocytes are retained by the leukocyte depletion medium (b) passing a wash fluid through the leukocyte depletion medium from the downstream surface through the upstream surface and, (c) passing the wash fluid through the leukocyte depletion medium from the upstream surface through the downstream surface via gravity.
