[Expression of regulatory T cells in thymus of myasthenia gravis patients].

Objective: To investigate the in situ expression of regulatory T cells (Tregs) in thymus and its significance for myasthenia gravis (MG).
Methods: Thirty nine MG patients who had not accepted immunosuppressive therapy before thymectomy were recruited as study group and 19 patients undergoing cardiosurgery as control. There was no significant statistical difference in age and gender between the two groups (P > 0.05). The location and proportion of Tregs in thymus were analyzed using indirect immunofluorescence double labeling immunohistochemistry and image analysis software.
Results: (1) Tregs were all located in medulla zone of thymus in control and MG groups. (2) Cells of germinal center had a high expression of CD25 and a low expression of CD4. It indicates that a majority of germinal center cells were B cells. (3) There were fewer Tregs around germinal center. (4) There was no statistical significant difference in absolute number of Tregs between the two groups (P > 0.05). But the proportion of Tregs was higher in control group (P < 0.05).
Conclusion: The proportion of thymus Tregs decreases in MG so as to weaken the function of immuno-regulation and suppression. This is probably a precipitating factor of MG.