Analytics of Functional Autoantibodies in Patients with Chagas Disease.

Autoantibodies directed against G-protein-coupled receptors (GPCR-AAB), an autoantibody type discovered in the 1970s, affect functionally their targets and are therefore called functional autoantibodies. GPCR-AAB are increasingly accepted as the origin or amplifier of various diseases. Here, we describe the present "gold standard" for measurement of GPCR-AAB in human blood. This bioassay monitors the chronotropic activity of GPCR-AAB by recording the spontaneous beating of cultured neonatal rat cardiomyocytes. The construction of this bioassay and its procedure and standardization for GPCR-AAB measurement are described in detail and also include the application of the bioassay for GPCR-AAB differentiation related to first the targeted receptors and IgG subclasses carrying the GPCR-AAB and second the extracellular receptor-binding site and specific epitopes targeted by the GPCR-AAB.