Therapeutic effects of interleukin-18 antibody on experimental autoimmune myasthenia gravis mice model

Objective To explore the potential therapeutic effects of interleukin (IL)-18 antibody on the experimental autoimmune myasthenia gravis (EAMG) mice model. Methods The classical active immunization methods were applied to establish the EAMG mice models. The control mice were administered with normal saline at the same amount. At the 70th day after immunization, the double-blind evaluation for the clinical scores by the Lennon criteria was used. A total of 36 EAMG mice with the scores 1-2 were chosen and divided to three groups randomly: the model mice treated with the intraperitoneal injection of normal saline, the IL-18 antibody treated mice and the prednisone acetate treated mice. The body weights measurement and the clinical scores evaluation were continued from the 70th day to the 90th day. At the 90th day, the blood samples were extracted from the caudal vein and used for detection of the levels of anti-acetylcholine receptor (AchR) total IgG, IgG1, IgG2b and the amounts of cytokines such as IL-4. Results At the 60th day after the experiment, the weight in the control mice was (20.28±0.93) g, in the model mice was (17.58±1.11) g, in the IL-18 antibody treated mice was (17.28±0.98) g, and in the prednisone acetate treated mice was (17.53±0.92) g. At the 90th day after the experiment, the weight in the control mice was (21.30±1.36) g, in the model mice was (16.67±0.97) g, in the IL-18 antibody treated mice was (19.25±0.82) g, and in the prednisone acetate treated mice was (19.33±0.72) g, suggesting the lower body weight in the model mice (t=4.331, P=0.000 8), while mice with IL-18 antibody (t=2.943, P=0.007 5) or prednisone acetate treatment (t=2.901, P=0.008 3) displayed recovery in the body weight. The clinical scores on the final day in the control mice were 0, in the model mice were 2.66±0.47, with statistically significant difference (t=5.389, P=0.000 5). The clinical scores in the IL-8 antibody or prednisone acetate treated mice were 0.54±0.51, 0.66±0.42, respectively. The serum contents of total IgG, IgG1 and IgG2b of anti-AchR in the control mice were 0.72±0.12, 0.60±0.10, 0.49±0.09, in the model mice were 3.85±0.29, 1.81±0.12, 0.99±0.07, all with statistically significant difference (total IgG, t=4.212, P=0.000 8; IgG1, t=4.105, P=0.000 9; IgG2b, t=3.798, P=0.001 1); in the IL-18 antibody treated mice were 0.90±0.14, 0.65±0.13, 0.57±0.06, in the prednisone acetate treated mice were 0.86±0.16, 0.69±0.12, 0.58±0.11, all restored to normal levels and having statistically significant differences compared with model mice (IL-18 treated mice: total IgG, t=4.322, P=0.000 7; IgG1, t=4.423, P=0.000 6; IgG2b, t=3.879, P=0.001 2. Prednisone acetate treated mice: total IgG, t=4.321, P=0.000 7; IgG1, t=4.012, P=0.000 9; IgG2b, t=3.654, P=0.001 4). The serum contents of IL-4, IL-10, IL-17 and IFN-γ in the control mice were 49.81±4.61, 84.42±7.34, 21.71±4.41, 116.32±10.11, in the model mice were 12.66±3.10, 22.23±6.03, 112.74±7.70, 307.82±18.10, in the IL-18 treated mice were 46.41±5.59, 75.07±18.97, 21.38±2.45, 124.84±17.65, and in the prednisone acetate treated mice were 44.60±5.46, 77.41±18.58, 19.63±4.48, 118.96±14.85. These data suggested the levels of IL-17 (t=4.678, P=0.000 5) and IFN-γ (t=4.022, P=0.001 2) were increased, whereas the levels of IL-4 (t=4.331, P=0.000 7) and IL-10 (t=4.108, P=0.000 9) were reduced in the model mice. Treatment with IL-18 antibody or prednisone acetate restored those antibodies and cytokines to normal level. Conclusion The results suggested that IL-18 antibody treatment rescued the clinical phenotypes of EAMG mice models by ameliorating the immune reactions. Key words: Myasthenia gravis, autoimmune, experimental; Disease models, animal; Interleukin-18; Antibodies; Prednisone