Correlation Between Levels Of IgG4 And IL-21 In Rats With Rheumatoid Arthritis

Objective:To investigate the expression of Immunoglobulin G4 and Interleukin-21 in serum and organizations from rats with rheumatoid arthritis,observe their change rule and correlation,further to explore the immune mechanism of disease.Methods:Totally 50 Wistar rats(150-180g)were randomly divided into normal group(n=20)and model group(n=30),model group was subjected to the bovine type II collagen to build rat model of collagen induced arthritis(CIA).CIA group were divided into four groups,respectively for the mice after 21,28,35,42 days after the first shot of immune emulsion,four groups were selected as negative control group,respectively for the rats sacrificed in four periods after first time injection of saline.Then collected blood and ankle specimens from each group.The enzyme-linked immunosorbent assay method was used to detect the content of Immunoglobulin G4 and Interleukin-21 in serum of rats,HE staining and immunohistochemical staining were applied to observed the synovial pathological score and the expression of IgG4,IL-21 and IL-21 receptor(IL-21r)in the ankle.Results:1.20 of 30 rats were success to build CIA models,the rate was 66.7%.2.Arthritis score in the model group were significantly higher than those in the control group(z=-2.805?-2.825?-2.825?-2.805,?P<0.05),3.The level of IL-21 was positively correlated with IgG4 in serum of rats(r= 0.404,P<0.05).4.The histopathological scores of rats in each model group were significantly higher than those in the control groups(z=-2.668?-2.660?-2.668?-2.660,P<0.05).5.The expression of IgG4 and IL-21r in the ankle joints of the CIA model significantly exceeded that in the negative group,and the expression of them in the model group had positive correlation(r=0.525,P<0.05).6.In model group rats,IL-21 content in serum was positively correlated with arthritis index,pathological grading and IL-21r expression in ankle joint(r=0.551,0.499,0.551,P<0.05),but serum IgG4 content had no obvious relevance with arthritis index,pathological grading and IgG4 expression in ankle;The IL-21r expression in CIA rats ankle was positively correlated with arthritis index and pathology score(r=0.528,0.569,P<0.05).IgG4 expression in ankles was positively correlated with pathological grading(r=0.547,P<0.05),meanwhile,it had no obvious correlation with arthritis index.Conclusions:1.The contents of IgG4 and IL-21 in the serum of the CIA model group were positively correlated,they were increased with the progress of the disease;2.The expression of IgG4 and IL-21 receptors in the ankle joint of the CIA model group was significantly higher than that in the control group,and the two showed a correlation and were closely related to the pathology score;3.Serum IL-21 level in the model group was closely related to the level of IL-21 receptor in the ankle joint;4.IL-21 may promote the occurrence and development of the disease by regulating the content of IgG4 in rheumatoid arthritis,they can provide a new direction for the pathogenesis and therapy of rheumatoid arthritis.