| Objective The present study was to detect autoantibody against M2-muscarinic acetylcholine receptor and investigate the effect of dexamethasone on the autoantibody in asthmatic rats.Methods Thirty-six healthy male wistar rats weighing 180-200g were randomly divided into three groups: normal control group,asthmatic model group, dexamethasone group, with 12 rats in each group. The asthmatic model was established by sensitizing and challenging rats with ovalbulium . The synthetic peptide M2-muscarinic acetylcholine receptor which corresponded to amino acids sequences of the second extracellular loop of human were used as antigens . Autoantibody against M2-muscarinic acetylcholine receptor were detected by SA-ELISA on 1st day,15th day,22nd day,29th day.Symptoms of asthmatic attack were observed in three groups. On 29th day ,all rats were killed, eosinophils were counted in the bronchial lavage fluid(BALF)and peripheral blood.then the right lungs were cut to make slides to observe inflammatory changes with microscrop.Results (1) Compared with dexamethasone group and normal control group, symptoms of asthmatic attack were obvious in asthmatic model group.(2) In asthmatic model group, the infiltration of inflammatory cells in lung, peripheral blood and BALF were severe,while it was mild in dexamethasone group. (3)On 29th day ,the rate of positive autoantibody against M2-muscarinic acetylcholine receptor in the serum from asthmatic model group(66.7%) were significantly higher than that of dexamethasone group(16.7%) and normal control group (8.3%),respectively.(4)The geometric mean of autoantibodies against M2-muscarinic acetylcholine receptor titer in asthmatic model group and dexamethasone group were 1:105and 1:30, respectively. In dexamethasone group, the rate of positive autoantibody and the titer of autoantibodies in the serum was lower than that of asthmatic model group . Conclusion:1. In asthmatic model group, the rate of positive autoantibody and the titer of autoantibodies against M2-muscarinic acetylcholine receptor in the serum have been kept in a very high level, which indicates that the antibody against M2-muscarinic acetylcholine receptor play a very important role in the pathogenesis of asthma.2. In dexamethasone group,not only the rate of positive autoantibody and the titer of autoantibodies against M2-muscarinic acetylcholine receptor in the serum decreased significantly ,but also the infiltration of inflammatory cells in lung, peripheral blood and BALF reduced significantly .It shows the inhibition of autoantibody against M2.muscarinic acetylcholine receptor can effectively prevent the development of asthma.
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