The Relationship Of CXCL13 And Myasthenia Gravis, And The Establishment Of EAMG Animal Model In Mice

Background Myasthenia gravis(MG) is a neuromuscular disease with an autoimmune etiology.It is mediated by acetylcholine receptor antibody,which directed against nicotinic acetylcholine receptor. Although progress has been made in studying for MG,it is still unknown by us about its real pathogenesis.B-lymphocyte is known to be the only kind of cell that could secrete antibody,and it plays a key role in humoral immunity,especially in the patients with seropositive myasthenia gravis (SPMG).Chemotatic factor is a group of protein,which can stimulate cells migrating to the target tissue.Chemotatic factors can be divided into CXC subfamily and CC subfamily according to the difference of primary structure in polypeptide chain.Chemotatic factors in CXC subfamily can effect neutrophilic granulocyte and stimulate lymphocyte obtaining chemotaxis.Chemotatic factors could bind with their specified receptors to produce a marked effect of chemotaxis.CXCL13 is confirmed to be important for the formation and targeting of B-lymphocyte.It is reported that CXCL 13 plays a key role in several autoimmune disease,but there is no report about the relationship between CXCL13 and MG disease.Experimental autoimmune myasthenia gravis animal model is an important tool to study pathogenesis of MG.There are several methods to establish the animal model at the moment,but none of these methods is perfect.Objective To elucidate the relationship among CXCL13,thymus and MG,the concentration in serum and thymus tissue of CXCL13 in MG patients have been tested by way of ELISA.And we also test the level of expression of the CXCL13 mRNA in thymus tissues by way of RT-PCR. At the same time,we transfer the thymus tissue to the nude mice in order to establish a kind of animal model about experimental autoimmune myasthenia gravis(EAMG) for the further study in MG.Methods 54 serum samples of patients with MG complicated with thymic hyperplasia were respectively collected in Xiangya hospital in one week post-treatment,one month post-treatment and pretherapy. The concentration in serum of CXCL13 is tested by ELISA.20 resected tissue samples of thymus of MG patients are examined by RT-PCR to observe the expression level of CXCL13.And the concentration in supernatant of thymic tissue culture of CXCL13 is also tested by ELISA. The fragments of hyperplasia thymic tissue were transferred into abdominal cavity of BALB/c nude mice in order to establish a kind of animal model about experimental autoimmune myasthenia gravis.And the methods of immunohistochemistry,transmission electron microscope, electromyogram and symptom observation were used to evaluate the animal model.Results The CXCL13 concentration in serum of MG patients in pretherapy is thicker than the normal people(p＜0.05),but it will decrease obviously one month after the treatment of glucocorticoid or thyectomy (p＜0.01).There is no difference of CXCL13 concentration between ocular MG patients and generalized MG patients(p＞0.05).The CXCL13 concentration in supernatant of hyperplasia thymic tissue culture of MG patients is thicker than that in normal thymic tissue(p＜0.01).And the level of CXCL13 mRNA expression in hyperplasia thymic tissue is also higher than the normal one.If we add dexamethasone into the culture fluid,we can observe that the CXCL13 concentration in supernatant becomes thinner(p＜0.01).The more the dexamethasone we add,the thinner the CXCL13 concentration will be.In the experiment of establishing animal models of EAMG,we obtain 9 mice presenting the symptoms of MG(9/25),and it is confirmed to fit the morphological features of human MG by way of immunohistochemistry,transmission electron microscope and electromyogram.Conclusions Because the serum CXCL13 concentration of MG patients is thicker than that in normal people,in addition,it will decrease obviously after treatment,we think that CXCL13 may be the serum maker of MG patients,and we could evaluate the effect of treatment and the prognosis by monitoring CXCL13 concentration in MG patients' serum.Because of over expression of CXCL13 mRNA in hyperplasia thymic tissue,which lead to increasing of CXCL13 concentration in supematant of hyperplasia thymic tissue culture,we think that the thymus may play a key role of MG.Dexamethasone could inhibit the expression of CXCL13 mRNA directly,and CXCL13 might be the new target of further research for the MG treatment.A new animal model of EAMG could be established by way of transplanting the fragment of hyperplasia thymic tissue into BALB/c nude mice,which might be a kind of new tool for the further research of MG,especially for the research of relationship between thymus and MG.