Identification of agonistic autoantibodies

Method for detecting disease-associated autoantibodies, which are directed at G protein-coupled receptors for diagnosis of autoimmune diseases, comprising

• a) bringing bodily fluid into contact with an agent for precipitating autoantibodies, wherein a fraction of said fluid comprising said autoantibodies is precipitated and wherein said autoantibodies are, upon precipitation, returned to essentially their native state,
• b) bringing the precipitated fraction into contact with a peptide comprising
• a sequence or partial sequence of the first and/or second loop of a G protein-coupled receptor and a tag, whereby a mixture is formed in which the autoantibodies bind said sequence or partial sequence of said peptide,
• c) incubating the mixture with a carrier coated with an anti-tag to bind said tag,
• d) washing the carrier,
• e) incubating the carrier with anti-IgG antibody subclasses, wherein the anti-IgG antibody is marked for an enzyme reaction or color reaction, and
• f) carrying out said enzyme reaction or color reaction
• to detect disease-associated autoantibodies, which are directed at said G protein-coupled receptor to diagnose said diseases,
• wherein the peptide that comprises a sequence or partial sequence of the first and/or second loop of the receptor is used in the detection of autoantibodies associated with dilatative cardiomyopathy, myocarditis, essential hypertension, refractory hypertension, pulmonary hypertension, or psoriasis, and that the peptide that comprises a sequence or partial sequence of the second loop of the receptor is used for Chargas' myocardiopathy, dilatative myocardiopathy, and/or Raynaud's syndrome.