Cytapheresis is an extracorporeal separation technique widely used in medicine for elimination of specific classes of blood cells from circulating blood. It has been shown recently to have clinical efficacy in various disease states, such as leukaemia, autoimmune disorders, rheumatoid arthritis, renal allograft rejection and sickle–cell anaemia. There are two major methods of extracorporeal leukocyte removal therapy in use in the clinical field, these are the centrifugal method, and the adsorptive method with fibre or beads. Leukocytapheresis using the leukocyte filter Cellsorba and granulocytapheresis using an Adacolumn has been proven to reduce leukocyte load in patients with rheumatoid arthritis and inflammatory bowel disease, but still has major limitations of specificity and selectivity. An ideal extracorporeal technique with non-thrombogenic materials and selective adsorption matrix is still in demand. Extracorporeal separation techniques can be improved by a combination of properties, such as mechanical properties of the column, an appropriate porosity of the matrix, biocompatibility of the polymer and chemical modification of the surface by immobilization of a ligand with an affinity towards target molecules or cells.
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