Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1992-03-13
1994-03-29
Dawson, Robert A.
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
210335, 210491, 210505, 210782, 210787, 210806, B01D 2702, B01D 3602, B01D 3900, B01D 2126
Patent
active
052981657
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for removing leukocytes and a filter system for removing the same. More particularly, the present invention is concerned with a method for removing leukocytes from a leukocyte-containing blood product, such as whole blood, a red cell product and a platelet product, and is also concerned with a filter system for removing leukocytes, which is useful for practicing the above-mentioned method.
BACKGROUND ART
In recent years, in the field of blood transfusion, a leukocyte-free blood transfusion in which leukocytes are removed from a blood product before transfusion is increasingly employed. This is because it has become apparent that side effects of transfusion, such as headache, nausea, chills and non-hemolytic feverish reaction, and side effects more serious to a recipient, such as allosensitization, post-transfusion GVHD (graft versus host disease) and viral infection, are mainly caused by leukocytes contained in a blood product employed in transfusion.
It is known that the number of leukocytes injected into a recipient at one transfusion must be limited to about 100,000,000 or less in order to avoid relatively slight side effects, such as headache, nausea, chills and fever. For meeting this requirement, leukocytes must be removed from a blood product to a level of 10.sup.-1 to 10.sup.-2 or less in terms of a leukocyte residual ratio. With respect to allosensitization, it now attracts the greatest attention in the art of blood transfusion, and it is one of the side effects, prevention of which is most desired. For preventing this serious side effect, it is believed that the number of leukocytes injected into a recipient at one transfusion must be limited to 5,000,000 or less, preferably 1,000,000 or less. For meeting this requirement, leukocytes must be removed from a blood product to a level of 10.sup.-4 or less in terms of a leukocyte residual ratio. With respect to post-transfusion GVHD and viral infection, no generally accepted standards for leukocyte-removal have been established. However, it is expected that infection with a virus, which is believed to exist only in leukocytes, such as cytomegalo virus, adult T cell leukemia virus and post-transfusion GVHD, could be prevented by removing leukocytes to a level of 10.sup.-4 to 10.sup.-6 or less in terms of a leukocyte residual ratio. Further, it is also expected that the probability of infection with a virus, which is believed to exist in both leukocytes and plasma, such as HIV, can be decreased by removing leukocytes.
The methods for removing leukocytes from a blood product can generally be classified into two methods. One is a method in which leukocytes are separated by a centrifuge, taking advantage of a specific gravity difference therebetween. The other is a filtering method in which leukocytes are removed by a filter comprising a fiber material or a spongy structure as a filter medium. In particular, a filtering method in which leukocytes are adsorption-removed by a non-woven fabric is widely employed due to the advantages of high capability to remove leukocytes, ease in handling and low cost.
Most of the conventional leukocyte-removing filters comprising a non-woven fabric are composed of two functionally different filter elements, i.e., a prefilter for removing aggregates, which has an average fiber diameter of from about 3 to 30 .mu.m and a relatively large pore size, and a main filter as an essential element for removing leukocytes, which is comprised of fibers having an average diameter of from about 1.7 to 3 .mu.m. With respect to the above-mentioned prefilter, it is preferably comprised of a plurality of layers in which the average fiber diameters and the pore sizes of the layers are decreased in the direction from a blood inlet toward a blood outlet (Japanese Patent Application Publication Specification No. 2-13588 and WO 89/03717). Aggregates are formed by aggregation of denatured blood components comprising fibrinogen, fibrin, denatured protein, nucleic acid and/or fat globule,
REFERENCES:
patent: 4416777 (1983-11-01), Kuroda et al.
patent: 4701267 (1987-10-01), Watanabe et al.
patent: 4925572 (1990-05-01), Pall
patent: 4936998 (1990-06-01), Nishimura et al.
Nishimura Takao
Oka Shin-Ichiroh
Asahi Medical Co., Ltd.
Dawson Robert A.
Kim Sun Uk
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