The invention relates to a blood treatment device configured to remove anti-neutrophil cytoplasmic antibodies (ANCAs) from the blood or blood plasma of a person in need thereof in an extracorporeal blood circuit, wherein the device comprises a matrix, and wherein said matrix comprises a monomeric form of proteinase 3 (PR3). The invention further relates to an extracorporeal blood circuit comprising a blood treatment device of the invention and to the blood treatment device for use as a medicament or for use in methods of treating a medical condition associated with ANCA.
