These results unambiguously prove that T. cruzi is able to induce a functional autoimmune response against the cardiovascular human ADRB1 through a molecular mimicry mechanism. Molecular mimicry between the immunodominant ribosomal protein P0 of Trypanosoma cruzi and a functional epitope on the human beta 1-adrenergic receptor. Subcutaneous abdominal adipose tissue of healthy non-obese subjects was microdialyzed with equimolar concentrations of dobutamine (selective beta 1-adrenoceptor agonist), terbutaline (selective beta 2-adrenoceptor agonist), or CGP 12177 (selective beta 3-adrenoceptor agonist). In these same nonfailing and failing left ventricles the respective beta 1-adrenergic receptor densities were 67.9 +/- 6.9 fmol/mg vs. 29.6 +/- 3.5 fmol/mg (P = 0.0001). Mapping of a functional autoimmune epitope on the beta 1-adrenergic receptor in patients with idiopathic dilated cardiomyopathy.