Filtration of platelet concentrates.

The transfusion of leukocyte-containing blood products causes a number of side reactions, which among others induces alterations of the immune system of the recipient leading to alloimmunization or immunosuppression. Antibodies against antigenic determinants of the major histocompatibility complex-proteins of class I are the major cause of alloimmunization. Though platelets are easy targets for HLA antibodies, they cannot induce the antibody production themselves. This requires leukocytes, carrying the MHC-proteins of the class II. Standard platelet concentrates for the clinical routine have more than 10(6) leukocytes. Leukocyte filters with a special surface modification reduce the number of leukocytes in platelet concentrates underneath this CILL-value (critical immunogenic load of leukocytes), thus reducing the antigenic, immunogenic effects of leukocyte contamination considerably.