Autoantibodies against the second extracellular loop of β1-adrenoceptor from patients with DCM in-hibit the proliferation of CD4＋ T lymphocytes by β1-adrenoceptor

Abstract

Objective To investigate the effects of autoantibodies （β1-AA） against second extra- cellular loop of the β1-adrenergic receptor （β1-AR-ECu ） in sera of patients with dilated eardiomyopathy （DCM） on proliferation of rat CD4＋ T lymphocytes. Methods 61-AA in the sera of patients with DCM was purified by affinity chromatography. CD4＋ T lymphocytes were isolated by immunomagnetic microbeads from peripheral blood mononuclear cells of rats and its positive rate was detected by flow cytometry. CCK-8 meth- od was used to detect the proliferation of CD4＋ T lymphocytes and flow cytometry was performed to measure the ratio of CD4＋/CD8＋ T lymphocyte. Results The purity of isolated rat CD4＋ T lymphocytes by immu- nomagnetic mierobeads reached 97.7%. The proliferation of CD4＋ T lymphocytes stimulated by CD3/CD28 was inhibited by β1-AA in a concentration-dependent manner. However, IgG antibodies extracted from sera of healthy controls did not suppress lymphocyte proliferation （P〉0.05）. The suppression effect of β1-AA was inhibited after binding to antigenic peptides corresponding to β1-AR-EC＋ and was completely blocked by metoprolol, a specific antagonist of β1-adrenergic receptor （β1-AR）. In addition, β1-AA had no effects on the ratio of CD4＋/CD8＋ T lymphocyte. Conclusion β1-AA isolated from DCM patients suppresses the pro- liferation of CD4＋ T lymphocytes through β1-AR pathway, which indicates that β1-AA can directly reduce the number of T lymphocytes and impair the function of T lymphocytes, resulting in immune system disorders and the development of DCM. Key words: β1-adrenergic receptor; Autoantibody; CD4＋ T lymphocyte