Complement factor based affinity chromatography

A method of purifying an antibody or a polypeptide from a mixture of polypeptides, wherein the antibody or the polypeptide comprises a C1q-binding part of an Fc-region, the method comprising the steps of:

• (i) applying the mixture to a C1q affinity column comprising an affinity chromatography ligand, the affinity chromatography ligand comprising a fusion polypeptide according to formula I
• TAG-X1-C1qA-X2-C1qB-X3-C1qC-X4 (formula I)
• wherein
• X1 denotes a first peptidic linker,
• X2 denotes a second peptidic linker,
• X3 denotes a third peptidic linker,
• X4 denotes a fourth peptidic linker,
• X1, X2, X3, X4 are independently of each other either present or absent,
• TAG is an amino acid sequence tag,
• TAG can be present or absent,
• C1qA has the amino acid sequence of SEQ ID NO:
• 07,
• C1qB has the amino acid sequence of SEQ ID NO:
• 08,
• C1qC has the amino acid sequence of SEQ ID No:
• 09, and denotes a peptide bond;
• (ii) eluting the antibodies or the fusion polypeptide.