Patent ID: 8900462

Claim:
A method for removing leukocytes from a leukocyte-containing liquid comprising: flowing a leukocyte-containing liquid through a leukocyte-removing filter, wherein the leukocyte-removing filter comprises: a container having a liquid inlet and outlet; and a porous filter material packed in the container, wherein the porous filter material has a permeation coefficient (kx) in the direction vertical to the filtration surface of 0.5×10 −12 m 2 to 2.0×10 −12 m 2 and a ratio (ky/kx) of a permeation coefficient (ky) in the direction parallel to the filtration surface to the permeation coefficient (kx) of 0.5 to 1.5; wherein the permeation coefficients (kx) and (ky) are calculated by using equation I: k =( dt/dp )×μ× v (I); wherein dt is the thickness of the porous filter material, v is the air flow rate, μ is the viscosity of the air, and dp is the pressure drop to be determined, wherein the container includes an inlet-side container having a liquid inlet and an outlet-side container having a liquid outlet, and wherein the inlet-side container and the outlet-side container sandwich the leukocyte-removing filter material directly or through a support to divide the inside of the filter into two compartments.