The Expression Of IL-21 In Peripheral Blood Of MG Patients And Its Correlation With Anti-AChR-Ab Class Switch

Objective:This study is aimed to explore the role of IL-21 in the pathogenesis of MG by detecting the concentrations of IL-21 in serum of MG and IL-21 receptor mRNA in PBMCs,measuring the expression of IL-21 receptor on the surface of B lymphocytes,at the same time detecting the expression level of serum anti-AChR-Ab and its isotype IgG₁,IgG₂,IgG₃ in MG patients and analyze the correlations of these items,so as to offer experimental proof for IL-21 targeted treatment of MG.Methods:26 patients and 18 healthy controls were investigated by retrospective study.The expression of IL-21R mRNA in PBMCs were detected by RT-PCR,the expression of IL-21R on B lymphocytes were measured by flow cytometry.The concentrations of serum IL-21 and the levels of anti-AChR-IgG and it's isotype IgG₁,IgG₂ and IgG₃ were tested by ELISA.Results:(1) The serum concentration of IL-21 in MG group was 31.686±8.499(pg/ml),and in control group was 15.147±6.366(pg/ml). Compared to the control group,the serum concentration level of IL-21 are obviously increased in MG group(P＜0.01).However the serum concentration of IL-21 in ocular MG subgroup was 29.834±6.354 (pg/ml),and in generalized MG subgroup was 34.648±10.839(pg/ml). The serum concentration of IL-21 presents no significant difference between the ocular MG subgroup and generalized MG subgroup (P＞0.05).(2) The relative OD values of IL-21R mRNA expressed on PBMCs was 0.139±0.052 in MG group,while it was 0.101±0.022 in control group,the expression of IL-21R mRNA in PBMCs are increased significantly in MG group(P＜0.05).Meanwhile,the relative OD values of IL-21R mRNA expressed on PBMCs was 0.129±0.039 in ocular MG subgroup,while it was 0.145±0.059 in generalized MG subgroup.There was no significant difference between the ocular MG subgroup and generalized MG subgroup(P＞0.05).(3) Furthermore,compare with the control group,the expression of IL-21R on B lymphocytes also increased in MG group(P＜0.05).(4) In anti-AChR-Ab positive MG group,the expression of IL-21R mRNA in PBMCs showed non-relevance with the levels of serum anti-AChR-IgG and it's isotype IgG₁,IgG₂ and IgG₃ respectively(P＞0.05),and the coefficient correlations were 0.198,0.188,-0.077,-0.241;however,the expression of IL-21R in B lymphocytes showed positive correlation with the levels of serum anti-AChR-IgG and it's isotype IgG₁ and IgG₃(p＜0.05, P＜0.01,P＜0.05),and the coefficient correlations were 0.719,0.885, 0.735,but non-relevance with IgG₂(P＞0.05),the coefficient correlation was 0.431.Conclusions:IL-21 might induce the class switch of anti-AChR antibodies to IgG₁ and IgG₃ isotype through IL-21R on B lymphocytes which promotes the pathogenesis of MG.