Abstract: The invention relates to diagnosing the presence or absence of antibodies, such as IgM, IgG or IgA antibodies, related to increased or decreased risk of developing Alzheimer's disease, using a phosphorylcholine conjugate. In addition, the invention relates to methods of immunization and prophylaxis, prevention and/or treatment of a subject against Alzheimer's disease, the method comprising the step of administering to the subject a pharmaceutical composition comprising at least one phosphorylcholine conjugate, or the step of administering to the subject an antibody preparation, for example a monoclonal antibody, with reactivity to a phosphorylcholine and/or a conjugate thereof.