- All 31 former COVID-19 patients had between 2 and 7 different GPCR-fAABs that acted as receptor agonists – Two functionally active autoantibodies, that were seen in almost all investigated former COVID-19 patients, were directed against the β2-adrenoceptor (β2-fAAB) and the muscarinic M2 receptor (M2-fAAB). These fAABs induced a positive and a negative chronotropic response on their targeted receptors, respectively. – Two other fAABs that were also present in 29 (90%) of the 31 investigated post-COVID-19 patients were directed against the angiotensin II AT1 receptor (fAT1-AAB) and the angiotensin 1-7 MAS receptor (MAS-AAB). These receptors belong to the renin angiotensin system (RAS) and cause a positive and negative chronotropic effect, respectively, when targeted by the respective fAABs. For the identification and characterisation of GPCR-fAABs, a bioassay was used, as described in great detail by Davideit et al.  and Wenzel et al.  for GPCR-fAABs against the beta1-adrenoceptor, and for other GPCR-fAABs by Wallukat et al. [30,35,36].