Disclosed is a use of a peptide immunogen, wherein the peptide is capable of generating antibodies reactive with a proteolytic cleavage site on IgG, in the preparation of a medicament for use in protecting a human subject from a pathological condition characterised by the release of a protease, wherein the pathological condition is a disease selected from an arthritic disease, a malignant disease, the presence of an infectious agent or a parasite, and a vascular disease.
