NK and Th17 cells in the thymus of myasthenia gravis patients

Abstract

Objective: As a classical autoimmune disorder, anti-acetylcholine receptor (AChR) antibody positive myasthenia gravis (MG) has an unconventional pathophysiology that involves thymus, the central organ for immune tolerance induction. Both natural killer (NK) cells and type 17 helper T (Th17) cells possess capacity to influence autoimmune inflammation. This study aims to determine the presence of Th17 and NK cells in the thymus from MG patients. Methods: Thymectomy materials of MG patients and non-MG controls were assessed by CD56, CD16, CD2, CD3, NKG2D, NKp46 and IL-23R flow cytometry and IL-23R, IL-21R, and ROR-γ immunohistochemistry. Results: Even though NK cell infiltration was limited, the majority of these cells displayed activation markers NKG2D and NKp46. Expectedly, the amount of CD2⁺ lymphocytic cells were higher than CD3⁺ thymocytes in which a considerable percentage was carrying the receptor for IL-23 (IL-23R). In addition to IL-23R, IL-21R, and ROR-γ were also detected in MG thymus as a marker related to Th17 cells. These Th17-related markers were reduced in thymoma compared to that of detected in thymic hyperplasia or the MG thymus with normal histopathology. Conclusion: Both NK cells and Th17 cells are found in the MG thymus indicating a possible cross-regulation between these cell types that may influence the course of autoimmune reactions.