The process for grafting (B) a porous element (1) for leukodepletion of a biological fluid such as blood or a blood component by adsorption and/or filtration, comprises impregnating (A) the porous element with a solution containing 0.01-5 wt.% of poly(ethylene oxide) (PEO) having same or different groups and an aqueous solvent, and applying an ionizing treatment to the porous element to assure covalent bypass grafting between the PEO and the porous element. The PEO (2) is a macromonomer whose group is polymerizable under the ionizing treatment, and has a molar mass of 800-2000 g/mol. The process for grafting (B) a porous element (1) for leukodepletion of a biological fluid such as blood or a blood component by adsorption and/or filtration, comprises impregnating (A) the porous element with a solution containing 0.01-5 wt.% of poly(ethylene oxide) (PEO) having same or different groups and an aqueous solvent, and applying an ionizing treatment to the porous element to assure covalent bypass grafting between the PEO and the porous element. The PEO (2) is a macromonomer whose group is polymerizable under the ionizing treatment, and has a molar mass of 800-2000 g/mol. The ionizing treatment is carried out by a plasma gas or a beam of electrons. The impregnation is carried out by sizing with a removal rate of 0.1-5 wt.% of the porous element. Independent claims are included for: (1) a porous element for leukodepletion of a biological fluid such as blood or a blood component by adsorption and/or filtration (2) a unit for the filtration of biological fluid such as blood or a blood component and (3) a system with sacs for leukodepletion of a biological fluid such as blood or a blood component.Linvention concerne un procédé de greffage dun élément poreux pour la déleucocytation par adsorption et/ou filtration dun fluide biologique tel que le sang ou un composant sanguin, ledit procédé comprenant les étapes prévoyant :-dimprégner lélément poreux avec une solution contenant un
