Abstract: The present invention relates to an isolated antibody or antigen-binding fragment thereof which specifically binds to mannose 6-phosphate and methods for preparing such antibody or antigen-binding fragment thereof. The invention further relates to a nucleic acid molecule encoding such antibody or antibody fragment, an expression vector comprising such nucleic acid molecule and a host cell comprising such nucleic acid molecule or expression vector. The invention also relates to a method for purifying or concentrating a target molecule comprising at least one mannose 6-phosphate residue from a sample. In another aspect, the invention relates to a method for diagnosing a disease which is characterized by an absent or reduced modification of molecules with mannose 6-phosphate residues.