The suppressive function of both CD4⁺CD25⁺Fas^lo and CD4⁺CD25⁺Fas^hi thymocytes of patients with MG is severely impaired. CD4⁺CD25^- T cells from MG or normal thymi were stimulated in the presence of irradiated allogenic T cell–depleted PBMCs in coculture with sorted autologous unfractionated CD4⁺CD25⁺ (▧) , CD4⁺CD25⁺Fas^hi (▦ ), or CD4⁺CD25⁺Fas^lo (▪) thymocytes at a ratio of 1:1. The results are expressed as a percentage of the proliferative response versus that obtained when adding the 2 separate populations (defined as 100%). The experiments were done with thymic cells from 2 patients with MG and 2 healthy controls. The results are expressed as the mean ± SEM of these 2 experiments.