Leukocyte removal method
A method of removing leukocytes that through reducing of clogging of a leukocyte removing filter element by blood cell components and plasma proteins being a problem encountered at the time of removing leukocytes from blood, shortens the filtration time at refrigerated filtration and exhibits high leukocyte removing performance at room temperature filtration. There is provided a method of removing leukocytes including filtering blood containing leukocytes through a leukocyte removing filter apparatus having multiple fibrous filter elements with different average fiber diameters to thereby remove leukocytes from the blood, characterized in that use is made of a leukocyte removing filter apparatus wherein the multiple fibrous filter elements include at least leukocyte removing filter element (A) of 2.0 to <4.0 μm average fiber diameter and leukocyte removing filter element (B) of 0.7 to 1.2 μm average fiber diameter and wherein the filter element (B) is disposed downstream of the filter element (A), the leukocyte removing filter element (B) having an average fiber diameter of >17.5% to <50% of that of the filter element (A).
1. A leukocyte removal method comprising filtering blood containing leukocytes using a leukocyte removal filter including plural fibrous filter materials having different average fiber diameters to remove the leukocytes in the blood, in which the fibrous filter materials include at least a leukocyte removal filter material A having an average fiber diameter of not less than 2.1 μm to less than 4.0 μm and a leukocyte removal filter material B having an average fiber diameter of not less than 0.7 μm to less than 1.2 μm, the filter material B is disposed downstream of the filter material A, and the average fiber diameter of the leukocyte removal filter material B is more than 17.5% to less than 50% of the average fiber diameter of the filter material A,
wherein the leukocyte removal filter has a geometric mean (X×Y) 0.5 of X and Y of not less than 0.5 to not more than 1 when a ratio (t a /t c ) of a filtration time at a temperature of 20 to 24° C. (t a ) to a filtration time at a temperature of 1 to 6° C. (t c ) is assumed to be X, and a ratio (r a /r c ) of a leukocyte removal filtration performance in the temperature of 20 to 24° C. (r a ) to a leukocyte removal filtration performance in the temperature of 1 to 6° C. (r c ) is assumed to be Y.
2. The leukocyte removal method according to claim 1 , wherein the leukocyte removal filter includes a leukocyte removal filter material C having an average fiber diameter of more than 1.2 μm to less than 2.0 μm and disposed between the filter material A and the filter material B.
3. The leukocyte removal method according to claim 1 , wherein the leukocyte removal filter includes the filter material A of which the weight in an effective filtration portion is not less than 2% to not more than 40% of the weight of the filter material B.
4. The leukocyte removal method according to claim 1 , wherein the leukocyte removal filter further includes a filter material A′ formed of the same material as the filter material A and disposed downstream of the filter material B, and the filter materials are symmetrically disposed with respect to a blood inlet side and a blood outlet side.
5. The leukocyte removal method according to claim 1 , wherein the blood has previously been stored at 1 to 6° C. and is filtered at 1 to 6° C.
6. The leukocyte removal method according to claim 1 , wherein the blood has been stored at 20 to 24° C. and is filtered at 20 to 24° C.