The invention concerns a filtering unit (1) intended to allow the leukoreduction of the blood or of a blood component, comprising an outer shell (2) provided with at least one inlet opening (3) and at least one outlet opening (4), the shell enclosing a porous element interposed between said openings, said porous element enclosing at least one prefilter (7) for eliminating the aggregates and at least one leukoreduction medium (8) for leukoreduction by adsorption and/or by filtration of the leukocytes, the prefilter (7) for eliminating the aggregates comprising at least one coherent non-woven web comprising a mixture of first discontinuous thermoplastic fibres and second discontinuous thermoplastic fibres of which the melting point is lower than that of said first fibres, said first and second fibres being linked to each other by thermal junctions.
