Antigen-specific T-cell activation in hyperplastic thymus in myasthenia gravis

Poor responses and adverse outcomes of myasthenia gravis after thymectomy: Predicting factors and immunological implications

Myasthenia gravis (MG) has been recognized as a series of heterogeneous but treatable autoimmune conditions. As one of the indispensable therapies, thymectomy can achieve favorable prognosis especially in early-onset generalized MG patients with seropositive acetylcholine receptor antibody. However, poor outcomes, including worsening or relapse of MG, postoperative myasthenic crisis and even post-thymectomy MG, are also observed in certain scenarios. The responses to thymectomy may be associated with the general characteristics of patients, disease conditions of MG, autoantibody profiles, native or ectopic thymic pathologies, surgical-related factors, pharmacotherapy and other adjuvant modalities, and the presence of comorbidities and complications. However, in addition to these variations among individuals, pathological remnants and the abnormal immunological milieu and responses potentially represent major mechanisms that underlie the detrimental neurological outcomes after thymectomy. We underscore these plausible risk factors and discuss the immunological implications therein, which may be conducive to better managing the indications for thymectomy, to avoiding modifiable risk factors of poor responses and adverse outcomes, and to developing post-thymectomy preventive and therapeutic strategies for MG.

Regulatory T cells in multiple sclerosis and myasthenia gravis

Multiple sclerosis (MS) is a chronic debilitating disease of the central nervous system primarily mediated by T lymphocytes with specificity to neuronal antigens in genetically susceptible individuals. On the other hand, myasthenia gravis (MG) primarily involves destruction of the neuromuscular junction by antibodies specific to the acetylcholine receptor. Both autoimmune diseases are thought to result from loss of self-tolerance, which allows for the development and function of autoreactive lymphocytes. Although the mechanisms underlying compromised self-tolerance in these and other autoimmune diseases have not been fully elucidated, one possibility is numerical, functional, and/or migratory deficits in T regulatory cells (Tregs). Tregs are thought to play a critical role in the maintenance of peripheral immune tolerance. It is believed that Tregs function by suppressing the effector CD4+ T cell subsets that mediate autoimmune responses. Dysregulation of suppressive and migratory markers on Tregs have been linked to the pathogenesis of both MS and MG. For example, genetic abnormalities have been found in Treg suppressive markers CTLA-4 and CD25, while others have shown a decreased expression of FoxP3 and IL-10. Furthermore, elevated levels of pro-inflammatory cytokines such as IL-6, IL-17, and IFN-γ secreted by T effectors have been noted in MS and MG patients. This review provides several strategies of treatment which have been shown to be effective or are proposed as potential therapies to restore the function of various Treg subsets including Tr1, iTr35, nTregs, and iTregs. Strategies focusing on enhancing the Treg function find importance in cytokines TGF-β, IDO, interleukins 10, 27, and 35, and ligands Jagged-1 and OX40L. Likewise, strategies which affect Treg migration involve chemokines CCL17 and CXCL11. In pre-clinical animal models of experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune myasthenia gravis (EAMG), several strategies have been shown to ameliorate the disease and thus appear promising for treating patients with MS or MG.

Influence of human myasthenia gravis thymus on the differentiation of human cord blood stem cells in SCID mice

The normal thymus contributes to T lymphocytes differentiation and induction of tolerance to self-antigens. Myasthenia gravis (MG) is characterized by abnormal thymic hyperplasia. To assess the potential influence of MG-thymus on the differentiation of T lymphocytes differentiation, we used the MG-thymus transplanted severe combined immunodeficiency (SCID) mice model to evaluate the human cord blood stem cells differentiation. Thymus fragments from MG patient and human cord blood stem cells were transplanted into SCID mice successively. SCID mice were observed to develop sustained human T lymphocytes and a functional anti-tumor immune. The levels of various T cell subsets in SCID mice with MG-thymus were different from that of control group. Among that, the frequency of CD4(+)CD25(+) T cells was significant lower in SCID mice with MG-thymus. The deficiency of CD4(+)CD25(+) T cells seens to contribute to the pathogenesis of MG.

Prolactin may be a promising therapeutic target for myasthenia gravis: hypothesis and importance

Myasthenia gravis (MG) is an autoimmune disease that affects the transmission signals from nerves to muscles. The basic pathology is the production of anti-acetylcholine receptor (AChR) antibodies (AChRAb) which is the consequence for the generation of autoreactive T lymphocytes responsing to AChR. However, the molecular mechanism of MG and the production of autoreactive T lymphocytes remain elusive. Recently beside its pivotal role in reproduction, the pituitary hormone prolactin (PRL) has been attributed to an immunomodulatory function. Furthermore it has been shown to be expressed in T cells and conversely it also affects the function of T cells, such as directly stimulating the proliferation and survival of T lymphocytes. In addition, elevated PRL levels frequently are described in autoimmune diseases, such as systemic lupus erythematosus (SLE) and multiple sclerosis (MS). So we hypothesized that the stimulating effect of PRL on T-cells function may be implied in the pathogenesis of MG and, perhaps, prolactin may be a promising therapeutic target for MG.