Proportion of Fas^hiCD4⁺, Fas^hiCD8⁺, Fas^hiCD4⁺ CD8, and Fas^hiCD4⁻CD8⁻ thymocytes among the whole population. (A) CD4 and CD8 expression was first analyzed in 7 controls and 26 MG patients. Data are mean ± SEM. As in Fig 1, two groups were distinguished according to their anti-AChR antibody titer: negative or borderline (<1 nmol/L) and positive (≥1 nmol/L). In this last group, CD4⁺ and double-negative cell proportions were significantly increased whereas the proportion of double-positive cells was significantly decreased, compared with controls. Using three-color immunofluorescence, Fas expression was analyzed in each population (CD4⁺, CD8⁺, CD4⁺CD8⁺, and CD4⁻CD8⁻); it allowed us to calculate the proportions of Fas^hiCD4⁺, Fas^hiCD8⁺, Fas^hiCD4⁺CD8⁺, and Fas^hiCD4⁻CD8⁻ thymocytes among the whole population. Differences were compared using the Mann-Whitney test. In the group of patients with positive anti-AChR antibody titers, the percentages of Fas^hiCD4 and Fas^hi CD4⁺CD8⁺ were significantly increased relative to controls.