Therapeutic and Immunoregulatory Effects of Tacrolimus in Patients with Refractory Generalized Myasthenia Gravis

Abstract

Objectives: The aim of this study wasto investigate the efficacy of tacrolimus treatment in patients with refractory generalized myasthenia gravis (MG) and explore its impact on lymphocytic phenotypes and related cytokines mRNA expression. Methods: A total of 24 refractory generalized MG patients were enrolled. Before treatment and at 2, 6, and 12 months after tacrolimus treatment, the therapeutic effect was evaluated by the quantitative MG score of the Myasthenia Gravis Foundation of America (QMG), Manual Muscle Test (MMT), MG-specific Activities of Daily Living (MG-ADL), 15-item Myasthenia Gravis Quality-of-Life Scale (MG-QOL15), and changes of prednisone dosage. Also, we used the flow cytometer for the lymphocytic immunophenotyping and real-time PCR for the qualification of cytokine mRNA in peripheral blood mononuclear cells (PBMCs) at different time points during the treatment. Results: Significantly decreased QMG, MMT, MG-ADL, and MG-QOL15 were observed at all time points during the tacrolimus treatment. The dosage of prednisone also reduced at the end of the observation period with only 6 adverse events reported. The immunological impact of tacrolimus was revealed by reduced percentages of Tfh, Breg, CD19⁺BAFF-R⁺ B cells, and increased percentages of Treg cells as well as down-regulated expression of IL-2, IL-4, IL-10, and IL-13 mRNA levels in PBMCs during the treatment. Conclusion: Our study indicated the clinical efficacy of tacrolimus in patients with refractory generalized MG. The underlying immunoregulatory mechanism of tacrolimus may involve alterations in the phenotypes of peripheral blood lymphocytes and Th1/Th2-related cytokine expression of PBMCs.