Dysfunctional Regulatory T Cells in Patients with Autoimmune Myasthenia Gravis: Therapeutic Targets? (PD6.006)

Abstract

Objective: To investigate circulating regulatory T cell (Treg) numbers and suppressive function in patients with autoimmune myasthenia gravis (MG). Background Published studies examining the role of Tregs in the pathogenesis of MG have reported conflicting results. In these investigations, isolation of Tregs was based on expression of CD25 alone, which is also expressed on a subset of recently activated and memory T cells. More recently, low expression of the IL-7Rα chain (CD127) combined with high expression of CD25 has allowed for isolation of pure Treg populations with high suppressive functionality. Design/Methods: The expression of surface CD4, CD25, and CD127, and intracellular Foxp3 was analyzed by flow cytometry in 16 MG patients vs. 14 normal control subjects. The function of Tregs (CD4+CD25highCD127low/- cells) was examined by co-culture experiments with CD25-negative autologous responder T cells (Tresp), and their suppressive capacity was determined in T cell proliferation assays. Expression of intracellular Foxp3 was assessed by flow cytometry, and cytokine profiles from the T cell culture supernatants were analyzed. GM-CSF was added to T cell co-cultures and the effects on Tregs investigated. Results: No alteration in the relative numbers of Tregs within the peripheral CD4+ T cell pool was seen in MG patients. A reduced expression of Foxp3 within Tregs, and a defect in the ability of these cells to suppress Tresp cells was demonstrated for both polyclonal and AChR-induced T cell proliferation. Cytokine profiles revealed altered levels of IL-6, IL-17, IFN-γ, and IL-10 in MG patients. The demonstrated defects in Treg function/phenotype were partially reversed by in vitro exposure to GM-CSF. Conclusions: The suppressive function of Tregs is impaired in MG patients, likely playing a role in the immunopathogenesis of the disease. Enhancement of Treg function in vitro is feasible, and may represent a novel therapeutic strategy in MG. Supported by: The NIH (National Institute of Neurologic Disorders and Stroke, K08NS058800, and the Muscular Dystrophy Association (MDA) MNM and JRS; and National Institute of Allergy and Infectious Diseases, RO1 AI 058190, BSP. This project was also supported by the University of Illinois at Chicago (UIC) Center for Clinical and Translational Science (CCTS), Award Number UL1RR029879 from the National Center For Research Resources. Disclosure: Dr. Meriggioli has received personal compensation for activities with Athena Diagnostics, Talecris Biotherapeutics, Gliknik, and Celegene Corporation. Dr. Meriggioli receives patent payments for a patent on bispecific antibody coated dendritic cells. Dr. Meriggioli has received research support from the NIH/NINDS and the Muscular Dystrophy Association. Dr. Muthusamy has nothing to disclose. Dr. Rowin has nothing to disclose. Dr. Sheng has nothing to disclose. Dr. Prabhakar has received personal compensation for activities with Gliknik Inc. as a consultant.Dr. Prabhakar has received research support from NIH.