Lymphocyte subsets of the peripheral blood in myasthenia gravis determined by two-color flow cytometry

Type B thymomas in patients with myasthenia gravis display a distinctive pattern of αβ TCR and IL-7 receptor α expression on CD4+CD8+ thymocytes

Thymoma is closely associated with myasthenia gravis (MG). However, due to the heterogeneity of thymoma and the intricate pathogenesis of MG, it remains unclear why some patients with thymoma develop MG and others do not. In this study, we conducted a comparative phenotype analysis of thymocytes in type B thymomas in patients with MG (MG (+) thymomas) and without MG (MG (-) thymomas) via fluorescence-activated cell sorting (FACS). Our results show that the developmental stages defined by the expression of CD3, CD4, and CD8 were largely maintained in both MG (+) and MG (-) thymomas, with CD4+CD8+ cells constituting the majority of thymocytes in type B thymoma, and no significant difference between this cell population was observed in MG (+) and MG (-) thymomas.We discovered that CD4+CD8+ thymocytes in MG (+) thymomas expressed low levels of αβ TCR and high levels of IL-7 receptor α (IL-7Rα), whereas in MG (-) thymomas, CD4+CD8+ thymocytes exhibited the opposite pattern of αβ TCR and IL-7Rα expression. These results suggest that the positive and negative selection processes of CD4+CD8+ thymocytes might differ between MG (+) thymomas and MG (-) thymomas. The expression of the Helios transcription factor is induced during negative selection and marks a group of T cells that have undergone negative selection and are likely to be deleted due to strong TCR binding with self-peptides/MHC ligands. We observed that the percentage of Helios-positive CD4SP T cells was greater in MG (-) than in MG (+) thymomas. Thus, the differentially regulated selection process of CD4+CD8+ thymocytes, which involves TCR and IL-7/IL-7Rα signaling, is associated with the presence of MG in type B thymomas.

Immune system and bone metabolism: Does thymectomy influence postmenopausal bone loss in humans?

Recent studies of animal models have suggested that an increase in the number of T cells due to both peripheral expansion and increased thymic T cell output plays a key role in the regulation of bone loss after ovariectomy. Osteoclastogenic cytokines which are either produced by T cells or activate T cells have also been implicated in ovx induced bone loss. Among them are TNF alpha and IL-7. The present study investigates the role of thymectomy (THX) and IL-7 in bone metabolism in humans. We studied T cells subsets, cytokine production and bone metabolism in 13 women thymectomized for Myasthenia gravis as compared to healthy controls. Our data demonstrate that the number of CD4+ and TNF-producing T cells is lower in THX women as compared to euthymic controls. However in THX women the residual T cells produce higher levels of IL-7 and RANKL. Furthermore, flow cytometry shows that IL-7 is produced by T and B cells. Serum levels of TNF alpha were unaffected by THX and both serum TNF alpha and the RANKL/OPG correlated inversely with BMD. There were no differences in bone turnover and bone mineral density between THX women and the controls. These data suggest that THX decreases the number of TNF-producing CD4+ T cells but does not alters serum TNF levels. The RANKL/OPG ratio and indices of bone metabolisms are also not affected by THX, although THX increases the levels of IL-7 and RANKL. Further studies are needed to clarify the role of thymus in bone metabolism and osteoclastogenesis in postmenopausal women.

Cell-surface expression of lymphocyte activation markers in myasthenia gravis

An analysis of the cell-surface expression of activation markers on B- and T-cells was done to compare patients with myasthenia gravis (MG) and healthy non-myasthenic controls. Marker expression was determined by immunostaining of peripheral blood mononuclear cells (PBMC) isolated from MG patients and from controls. The percentage of B-cells in PBMC that expressed CD71, a transferrin receptor, was significantly greater in patients compared to controls, particularly, in patients who were seropositive for acetylcholine receptor-specific antibodies. When subgroups of MG patients were studied, our data showed that within the first year after disease onset, patients had a significantly higher percentage of T-cells in PBMC that were CD25+ (interleukin-2 receptor alpha) and CD26+ (dipeptidyl peptidase IV ectoenzyme) in comparison to patients with disease symptoms for longer than one year and to healthy controls. Our data also showed that patients with generalized MG had significantly lower percentages of gamma/delta T-cells in peripheral blood compared to healthy controls. The results of this study demonstrate important differences in the cell-surface expression of lymphocyte markers between MG patients and healthy non-myasthenic controls. In addition, differences between subgroups of patients demonstrate that patients with MG are heterogeneous in clinical presentation and in immunological parameters.

Change of immunological parameters in the clinical course of a myasthenia gravis patient with chronic graft-versus-host disease

The change in immunological parameters was studied during the clinical course of a myasthenia gravis (MG) patient with chronic graft-versus-host disease (GVHD), which developed after bone marrow transplantation from an HLA-identical donor. Anti-acetylcholine receptor antibody gradually decreased in the patient treated with immunosuppressive agents, but was not detected in the donor. Lymphocyte numbers were low just before the onset of MG, increased abruptly within several days and then gradually decreased with treatment. The percentage of CD3+ and CD19+ lymphocytes was higher at onset than before, the percentage of CD4+ cells was higher at onset and gradually decreased with treatment, while CD8+ cells showed the lowest level just before onset and gradually increased during the clinical course. CD4+/CD45RA- cells also showed the highest levels at onset and a gradual decrease with treatment. Cellular, as well as humoral immune responses, might be associated with the pathogenesis of MG with chronic GVHD.

Changes in peripheral blood lymphocyte subset frequencies in myasthenia gravis patients are related to immunosuppression

Surface antigens on peripheral blood lymphocytes from myasthenia gravis patients were investigated. The expression of DR+ and CD8+/DR+ T lymphocytes was increased and the expression of CD4+ T cells reduced. Neither thymectomy, clinical condition nor anti-acetylcholine receptor antibody titre correlated with any of the changes in peripheral blood lymphocyte subsets observed. However, immunosuppressive therapy correlated with the significant reduction in CD4+ and CD2+/CD4+ T cells in these patients.