Effect of an agonistic anti-Fas antibody on MG Fas^hi thymocytes. (A) Fas and CD3 expression was analyzed after 20 hours of culture in the presence of immobilized CH-11 anti-Fas antibody (5 μg/mL) and in control conditions. A representative analysis of an MG patient is shown. After anti-Fas treatment a decrease in the proportion of Fas^hi thymocytes with intermediate CD3 expression was observed. (B) Living cell numbers (measured by Trypan blue assay) obtained with and without CH-11 anti-Fas antibody were compared in three MG patients. Cell numbers in CD3^intFas^lo and CD3^intFas^hi thymocytes were calculated from percentages obtained by immunofluorescence analysis. Although CD3^intFas^lo were not sensitive to CH-11 anti-Fas antibody, most CD3^intFas^hi were eliminated in this condition. Data are the mean ± SEM from three experiments.