T and B lymphocytes reacting with the extracellular loop of the beta 2-adrenergic receptor (beta 2AR) are present in the peripheral blood of patients with myasthenia gravis.
Academic Article
Overview
abstract
Eighteen percent of patients with myasthenia gravis (MG) have serum antibodies against a synthetic peptide corresponding to the second extracellular loop of the human beta 2AR (residues 172-197). In this study we examined T and B cell responses to the peptide, using assays to detect individual cells secreting interferon-gamma (IFN-gamma) and IL-4 or antibodies against the peptide, and by measuring thymidine incorporation in response to the peptide. The peptide from the beta 2AR induced cytokine secretion from blood mononuclear cells in 67% of MG patients, compared with 14-28% of the control groups. Cells secreting antibodies binding to the peptide were present in 54% of MG patients and in 19-28% of controls. The numbers of beta 2AR-reactive cells were higher in MG patients than in controls. Peptide-induced increase in thymidine incorporation in cells was also more frequently demonstrated in patients (26%) compared with controls (about 10%). Activation of cells was dependent on monocytes and on MHC class II DR antigen. Based on the pattern of the cytokine secretion induced, beta 2AR-reactive T cells comprise both T helper type-1 and type-2 subsets. In addition, control peptide-reactive T and B cells were much less frequently demonstrated in the patients, and the number of such cells did not differ between the groups. Our results show that beta 2AR-reactive cells are present in most patients with MG. Such autoreactive antibodies and cells might play a role in the pathogenesis of the disease by influencing the function of skeletal muscle and immune systems.
