Increased thymocyte differentiation in myasthenia gravis: A dual‐color immunofluorescence phenotypic analysis

Thymocytes express multiple, different surface antigens according to their stage of maturation. Surface differentiation antigens have been studied with the technique of simultaneous dual‐color, direct immunofluorescence in the thymuses of 20 patients with myasthenia gravis (MG) and 10 control subjects with cardiac diseases. Fluorescein isothiocyanate‐conjugated and phycoerythrin‐conjugated monoclonal antibodies were used to stain thymic cell suspensions. A significant decrease in the percentage of immature and common thymocyte phenotypes (CD1+,3+ and CD4+,8+) and significant increase in the percentage of mature thymocyte phenotypes (CD1‐,3+; CD4+,8‐; and CD4‐,8+) and of B cells (CD20+) were found in MG thymuses compared with controls. These data, indicating an increased availability of mature, fully immunocompetent T and B cells, indirectly suggest the occurrence of an active immune response in MG thymus.