Abstract: The present disclosure relates to binding compounds/antibodies that bind to the second extracellular loop of the human ?1-adrenoreceptor (?1-AR-ECII) that are produced by/obtainable from a host cell/hybridoma with a deposit number selected from the group consisting of DSM ACC3121, DSM ACC3174, DSM ACC3175, DSM ACC3176 and DSM AC-C3177. The binding compounds/antibodies are particularly useful in determination of auto-anti-?1-AR antibodies in an in vitro cell based assay system in order to characterize and to identify auto-antibodies directed against the ?1-AR-ECII in a biological sample. Further aspects of the disclosure are nucleic acid molecules encoding said binding compounds/antibodies, vectors, host cells, methods for producing the binding compounds/antibodies of the disclosure as well as a kit comprising the binding compounds/antibodies of the present disclosure.