Search

Background: Activating autoantibodies (AAb) to adrenergic receptors (AR) have previously been reported in patients with postural tachycardia syndrome (POTS). These AAb may contribute to a final common pathway for overlapping disease processes, reflecting a possible autoimmune contribution to POTS pathophysiology. In prior studies, measurement of AAb activity was inferred from costly, low-throughput, and laborious physiological assays. In the present study, we developed and validated an alternative cell-based bioassay for measuring AAb activity in serum by means of pre-treatment with monoamine oxidase (MAO). Methods: A total of 37 POTS patients and 61 sex-matched healthy control participants were included. Serum was pre-treated with MAO to remove endogenous catecholamines that could falsely inflate AR activation by AAb. A receptor-transfected cell-based bioassay was used to detect presence of α1AR-AAb and β1AR-AAb in serum. Results: MAO effectively degraded catecholamines as demonstrated by suppression of norepinephrine-induced α1AR activation in POTS (6.4 ​± ​0.7 vs. 5.5 ​± ​0.9; P ​= ​0.044) and in controls (4.1 ​± ​0.5 vs. 3.9 ​± ​0.6; P ​= ​0.001). Mean activity values were greater in the POTS vs. Controls for α1AR-AAb (6.2 ​± ​1.2 vs. 5.3 ​± ​1.0; P ​