Activation state of Fas^lo and Fas^hi thymocytes. Freshly isolated thymocytes were stained with anti-Fas antibody and PE-labeled anti-CD25 or FITC-labeled anti-HLA-DR. (A) In Fas expression analysis, gates were set to define Fas^lo and Fas^hi thymocytes. During the acquisition step, events were accumulated in these gates. Analysis of one representative MG patient (anti-AChR antibody titer 33 nmol/L) is shown. In this representative analysis (one of six experiments) the percentage of HLA-DR–expressing or CD25-expressing cells is strikingly higher in Fas^hi thymocytes than in Fas^lo thymocytes. (B) Such analyses were performed on 6 controls and 6 MG patients. Data presented are mean ± SEM. The increase in HLA-DR or CD25⁺ cells in Fas^hi thymocytes compared with Fas^lo thymocytes were similar in controls and in MG patients.