Monoclonal antibody analysis of blood T-cell subsets in myasthenia gravis

CD8+ T-Cell Deficiency, Epstein-Barr Virus Infection, Vitamin D Deficiency, and Steps to Autoimmunity: A Unifying Hypothesis

CD8+ T-cell deficiency is a feature of many chronic autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, Sjögren's syndrome, systemic sclerosis, dermatomyositis, primary biliary cirrhosis, primary sclerosing cholangitis, ulcerative colitis, Crohn's disease, psoriasis, vitiligo, bullous pemphigoid, alopecia areata, idiopathic dilated cardiomyopathy, type 1 diabetes mellitus, Graves' disease, Hashimoto's thyroiditis, myasthenia gravis, IgA nephropathy, membranous nephropathy, and pernicious anaemia. It also occurs in healthy blood relatives of patients with autoimmune diseases, suggesting it is genetically determined. Here it is proposed that this CD8+ T-cell deficiency underlies the development of chronic autoimmune diseases by impairing CD8+ T-cell control of Epstein-Barr virus (EBV) infection, with the result that EBV-infected autoreactive B cells accumulate in the target organ where they produce pathogenic autoantibodies and provide costimulatory survival signals to autoreactive T cells which would otherwise die in the target organ by activation-induced apoptosis. Autoimmunity is postulated to evolve in the following steps: (1) CD8+ T-cell deficiency, (2) primary EBV infection, (3) decreased CD8+ T-cell control of EBV, (4) increased EBV load and increased anti-EBV antibodies, (5) EBV infection in the target organ, (6) clonal expansion of EBV-infected autoreactive B cells in the target organ, (7) infiltration of autoreactive T cells into the target organ, and (8) development of ectopic lymphoid follicles in the target organ. It is also proposed that deprivation of sunlight and vitamin D at higher latitudes facilitates the development of autoimmune diseases by aggravating the CD8+ T-cell deficiency and thereby further impairing control of EBV. The hypothesis makes predictions which can be tested, including the prevention and successful treatment of chronic autoimmune diseases by controlling EBV infection.

Altered expression of costimulatory molecules in myasthenia gravis

To characterize the involvement of costimulatory pathways in the pathogenesis of myasthenia gravis (MG), a multiparameter flow cytometry assay was adopted to enumerate blood mononuclear cells (MNC) expressing CD28, CD80, CD86, CD40, and CD40L molecules in patients with MG and healthy subjects. Patients with MG had lower percentages of CD8(+)CD28(+) cells, augmented percentages of CD4(+)CD80(+), CD4(+)CD86(+), CD8(+)CD80(+), CD8(+)CD86(+), CD14(+)CD80(+), and CD14(+)CD86(+) cells, and similar levels of cells expressing CD40 and CD40L and of B cells expressing CD80 and CD86 compared to the controls. Patients with early onset of MG (<40 years) had lower percentages of CD3(+)CD86(+), CD4(+)CD86(+), CD8(+)CD86(+) T cells and CD20(+)CD86(+) B cells compared to those with late onset (>40 years). There was a positive correlation between the patients' age and percentages of CD86(+) cells. The data indicate that the CD28/CD80-CD86 costimulatory pathway is involved in MG. The high percentages of CD80 and CD86 positive T cells and monocytes may reflect persistent activation of T and B cells, whereas the low CD28 expression may be the result of chronic exposure to CD80 and CD86. These molecules could be the focus for new and improved immunomodulating therapies of MG.

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.

Ocular myasthenia: a protean disorder

Ocular myasthenia is a localized form of myasthenia clinically involving only the extraocular, levator palpebrae superioris, and/or orbicularis oculi muscles. Ocular manifestations can masquerade as a variety of ocular motility disorders, including cranial nerve and gaze palsies. A history of variable and fatiguable muscle weakness suggests this diagnosis, which may be confirmed by the edrophonium (Tensilon) test and acetylcholine receptor antibody titer. Anticholinesterases, corticosteroids and other immunosuppressive agents, and other therapeutic modalities, including thymectomy and plasmapheresis, are used in treatment. As the pathophysiology of myasthenia has been elucidated in recent years, newer treatment strategies have evolved, resulting in a much more favorable prognosis than several decades ago. This review provides historical background, pathophysiology, immuno-genetics, diagnostic testing, and treatment options for ocular myasthenia, as well as a discussion of drug-induced myasthenic syndromes.

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.

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

Lymphocyte subsets of the peripheral blood in 43 patients with myasthenia gravis (MG) were determined by two-color flow cytometry using a number of monoclonal antibodies. In the MG patients without thymectomy (Tx) and prednisolone (PSL) treatment, lymphocyte counts, B-cells, CD4+ cells and their subsets were normal, but numbers of T-cells, CD8+ cells and CD8+ CD 11-subsets were significantly decreased. Furthermore, proportions of activated cells in T-cells, CD 16+ Leu7- and CD16+ Leu7+ NK subsets were significantly high in the patients. The changes in T-cells, CD8+ cells and activated T-cells were less marked in the MG patients than Sjögren's syndrome (SS) used as a disease control. Contrary to MG patients, lymphocyte counts, CD4+ cells and their subsets were decreased, and the proportions of B-cells were high in SS patients. These results suggest altered immunologic conditions, immunologically active and deficient conditions, in both diseases, although the alterations were more prominent in SS than MG. PSL treatments and Tx significantly altered the lymphocyte profiles: PSL decreased lymphocytes, B-cells, T-cells, CD4+ cells and their subsets, while the proportions of CD8+ cells were increased. The changes were compatible with the known immunosuppressive effects of PSL. After Tx, lymphocytes and B-cells decreased, but the proportions of T-cells, CD8+ cells and their subsets, and NK cells subsets returned toward normal. CD4+ CD8+ cells were not increased in MG patients, and the cells did not decrease after Tx. Some of these observations might be relevant to clinical effects of Tx, although the mechanism responsible for these changes is still unknown.

Phenotypic characteristics of thymic B lymphocytes in myasthenia gravis

We have found prominent secretion of immunoglobulin and anti-acetylcholine antibodies by thymic lymphocytes (TL) of myasthenics despite a relative paucity of B (surface IgM+) cells in such TL. To determine whether there was a surface IgM- B cell in the TL which could manifest such responses, we compared the frequency of cells expressing the B cell-specific phenotypic marker CD20 (B1+), surface IgM (SIgM+), surface IgG (SIgG+), and surface IgD (SIgD+) in TL and autologous blood mononuclear cells in 36 myasthenic patients. B1+ cells were significantly more frequent than SIgM+ cells in TL (3.2 +/- 0.6 vs 0.6 +/- 0.2). In double-labeling studies, less than 25% of the B1+ cells coexpressed SIgM. Only 0.3% of the TL were SIgD+. In contrast, the frequencies of B1+ and SIgM+ cells in autologous blood were not significantly different (10.7 +/- 1.3 vs 8.2 +/- 0.8%). About 75% of blood B1+ cells co-expressed SIgM. These findings suggest that mast B cells in these TL have undergone isotope switching during prior in vivo differentiation and could manifest the observed humoral responses.

[Study of circulating lymphocytes by monoclonal antibodies in myasthenia gravis]

A significant decline of CD3 cell detected by rosettes and a significant increased of B cell populations were observed. The total CD3+, helper CD4+ and suppressor CD8+ T-cell subsets showed no significant variation em relation to sex, age thymectomy and corticotherapy by monoclonal antibodies.

Evaluation of immunoregulatory cells in Duchenne muscular dystrophy and spinal muscular atrophy among African and Indian patients

Suppressor cells were assayed by numerical and functional tests in Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA) among African and Indian children in order to contribute to an understanding of the pathogenesis of these neurological disorders. Peripheral blood mononuclears (PBM) were classified as total T cells and T cell subsets by the OKT series of monoclonal antibodies and as B cells by the presence of surface immunoglobulin. The suppressive effects of PBM pretreated with concanavalin A (Con A) on normal homologous phytohaemagglutinin (PHA) transformation of mononuclear cells was determined. PBM stimulation by PHA was also assessed. Patients with DMD had a significant increase (P = 0.0353) in the number of T suppressor/cytotoxic cells (1218 +/- 142 cells/mm3, mean +/- SE) as compared to controls (815 +/- 95 cells/mm3) and a significant reduction (P = 0.0282) in OKT4+ cells expressed as a percentage of OKT3+, 50% +/- 3 compared to 61% +/- 3. No differences were detected in any of the numerical assays employed in SMA as compared to controls, or within SMA patients according to severity of disease. Suppressor function and PHA transformation were normal in both groups of patients. No significant correlations were detected between numerical and functional assays of suppression. The implication of the results obtained for the role of immunoregulatory cells in the pathogenesis of DMD in these children is discussed.

Acquired disorders affecting the immune system and non-Hodgkin's lymphoma

A case-control study was undertaken to determine whether a prior history of a variety of acquired disorders affecting the immune system was associated with an increased risk of non-Hodgkin's lymphoma. Cases were identified over a 4-year period (1976-1979) at the Johns Hopkins Hospital and individually matched to hospital controls on age, sex, race, and year of diagnosis. For the 109 cases and matched controls who were traced and interviewed, positive associations suggesting an increase in risk were not detected. Instead, there was a suggestion of an inverse relationship. Odds ratios (ORs) were consistently less than 1 for associations between non-Hodgkin's lymphoma and several chronic infectious diseases (OR = 0.65, 95% CI = 0.35, 1.20), chronic inflammatory diseases (OR = 0.88, 95% CI = 0.43, 1.79), autoimmune disorders (OR = 0.80, 95% CI = 0.19, 3.76), and allergic disorders (OR = 0.77, 95% CI = 0.45, 1.32). A statistically significant protective association was found for surgical removal of lymphoid tissue (OR = 0.50, 95% CI = 0.27, 0.91). Adjustment for potentially confounding variables did not change these results. These findings do not support the previously anecdotally reported impression that disorders producing a chronic antigenic stimulus are associated with the development of non-Hodgkin's lymphoma.

A double-label flow cytometric analysis of the simultaneous expression of OKT4 and Leu2a antigens on circulating T lymphocytes in myasthenia gravis

A two-color immunofluorescence analysis of circulating abnormal T lymphocytes bearing both helper (T4) and suppressor/cytotoxic (Leu2a) T cell markers (double marker cells) was performed by means of the laser flow cytometry system. The double marker cell level was very low in 6 patients with multiple sclerosis and 12 normal controls studied. Fifteen of 31 patients with myasthenia gravis (MG) showed an elevation of double marker cells without an increase in T6-positive cells. The values were significantly higher in patients with thymoma or thymic hyperplasia than in those with a normal thymus. The double marker cell level was considered to reflect thymic abnormality in MG and to be helpful for determining the indication of thymectomy.

Effect of thymectomy on blood T-cell subsets in myasthenia gravis

We studied peripheral blood mononuclear T-cell subsets in 23 patients with myasthenia gravis who had undergone thymectomy at least one year before study. An increase in the T4+/T8+ (helper-inducer/suppressor-cytotoxic cell) ratio was seen, similar to that previously reported in nonthymectomized patients with myasthenia gravis. Six patients were studied before and after thymectomy and no consistent alteration in the pattern of T-cell subsets was detected. We were not able to demonstrate a quantitative effect of thymectomy on peripheral blood mononuclear T-cell subsets in patients with myasthenia gravis.

Glucocorticoid receptors of mononuclear leukocytes from myasthenia gravis patients

The present study was performed to analyse glucocorticoid receptor (GR) binding in peripheral blood mononuclear leukocytes (MNL) from 39 myasthenia gravis (MG) patients (unoperated patients (n = 13), thymectomized patients (n = 14) and patients receiving glucocorticoids: thymectomized (n = 11) and unoperated (n = 6]. A whole cell binding assay with 3(H) dexamethasone was used. GR mean values were significantly higher in the MNL of MG patients (thymectomized or not) not receiving glucocorticoid than in the MNL of healthy donors. Affinity was within the normal range. Sex, age or clinical forms of illness did not influence the results. In patients receiving prednisone (Pd) the GR values were significantly lower than in MG patients without Pd therapy, independent of Pd dose or time of administration. No differences in receptor binding between normal subjects and MG patients receiving Pd have been found.

Circulating T cell subsets in the Lambert-Eaton myasthenic syndrome

Peripheral blood T cell subsets were measured using monoclonal antibodies and a fluorescence activated cell sorter in 15 untreated patients with Lambert-Eaton myasthenic syndrome (nine with small cell carcinoma, one undifferentiated epithelial tumour (ca-LEMS], five with no demonstrable tumour (non-ca-LEMS), 10 age-matched healthy controls and 10 patients with small cell carcinoma without neurological disease. OKT8+ (suppressor/cytotoxic) T cells were significantly decreased in ca-LEMS compared with non-ca LEMS (p less than 0.001) ca-controls (p less than 0.01) and healthy controls (p less than 0.001). In one patient depressed OKT8+ T cells antedated clinically evident tumour by five months. OKT3+ (total) and OKT4+ (helper) T cells were similar in ca-LEMS, non-ca LEMS and controls. The mechanism underlying the loss of circulating OKT8+ T cells in ca-LEMS is unknown, but these changes may help to predict the presence of carcinoma in this disease.

Myasthenia gravis: reactivation of clinical disease and of autoimmune factors after discontinuation of long-term azathioprine

In 15 patients with myasthenia gravis who were in stable clinical remission while receiving azathioprine, we monitored disease severity and serial autoantibody titers before and after discontinuation of azathioprine. Cellular immunoreactivity against tuberculin (PPD) and against Torpedo acetylcholine receptor (AChR) was measured serially in 11 patients. Eight of 15 patients (53%) had a clinical relapse after 3 to 11 months, necessitating the reinstitution of immunosuppressive treatment in 6 patients. Seven patients have remained clinically stable during an observation period of 20 to 40 months. Anti-AChR autoantibody titers correlated closely with the clinical course in the majority of patients, and rose markedly in 7 of the 8 patients who relapsed. Cellular stimulation indices correlated less closely with the clinical severity. Only in 3 patients did the clinical score, antibody titer, and cellular stimulation index rise concurrently. In 4 patients who had high cellular stimulation indices after the discontinuation of azathioprine, it was possible to isolate AChR-reactive inducer/helper T lymphocytes.

Myasthenia gravis and myasthenic syndromes

More than a decade ago myasthenic symptoms were observed in rabbits immunized with acetylcholine receptor (AChR) [119] and AChR deficiency was found at the neuromuscular junction in human myasthenia gravis (MG) [36]. By 1977 the autoimmune character of MG and the pathogenic role of AChR antibodies had been established by several measures. These included the demonstration of circulating AChR antibodies in nearly 90% of patients with MG [87], passive transfer with IgG of several features of the disease from human to mouse [149], localization of immune complexes (IgG and complement) on the postsynaptic membrane [30], and the beneficial effects of plasmapheresis [20, 123]. Substantial subsequent progress has occurred in understanding the structure and function of AChR and its interaction with AChR antibodies. The relationships of the concentration, specificities, and functional properties of the antibodies to the clinical state in MG have been carefully analyzed, and the mechanisms by which AChR antibodies impair neuromuscular transmission have been further investigated. The clinical classification of MG has been refined, the role of the thymus gland in the disease has been further clarified, and new information has become available on transient neonatal MG. The prognosis for generalized MG is improving, but there is still no consensus on its optimal management. Novel therapeutic approaches to MG are now being explored in animal models. Recognition of the autoimmune origin of acquired MG also implied that myasthenic disorders occurring in a genetic or congenital setting had a different cause. As a result, a number of congenital myasthenic syndromes have come to be recognized and investigated. Finally, an acquired disorder of neuromuscular transmission different from MG, the Lambert-Eaton myasthenic syndrome, has also been shown to have an autoimmune basis. In this syndrome, active zone particles of the presynaptic membrane are direct or indirect targets of the pathogenic autoantibodies.

A case of myasthenia gravis associated with optic neuritis

A case of myasthenia gravis is described in association with optic neuritis in which brain-stem auditory and somatosensory evoked potentials were normal. CSF contained alkaline oligoclonal IgG bands. Blood lymphocyte subpopulations showed a decreased number of T-suppressor cells.

Corticosteroid effects on circulating lymphocyte subset levels in normal humans

The effects of in vivo corticosteroid administration on levels of lymphocyte subsets in normal humans require further definition. Using monoclonal antibodies, we carried out a double-blind, placebo-controlled study of oral and intravenous methylprednisolone in 10 normal volunteers. Four hours after a 7-day oral course of 0.5 mg/kg/day, there was modest lymphopenia but no significant selective alteration in lymphocyte subsets. In contrast, 4 hr after a single intravenous injection of 1.0 mg/kg, there was more pronounced lymphopenia (P less than 0.01), a selective, relative decrease in T4 cells (P less than 0.001), and a more modest decrease in the percentage of T3 cells. The possible mechanisms and implication of these changes are discussed.

IL-2 secretion by soluble antigen-reactive human T-cell clones

Human tetanus toxoid specific T-cell lines and clones capable of producing IL-2 were established. IL-2 production occurred only when the antigen-specific T cells were cultured with both tetanus toxoid antigen and an autologous, irradiated adherent cell population. The T-cell lines and clones remained strictly dependent on exogenous IL-2 for proliferation at all other times. Phenotypic characterization with monoclonal antibodies recognizing T-cell subsets revealed that the antigen-specific lines and clones bore predominantly OKT3 and OKT4 markers with essentially no OKT8 positive cells present. T-cell clones which were demonstrated to secrete IL-2 activity could also partially deplete media of IL-2 if cultured in the absence of soluble antigen and irradiated adherent cells.

The effect of plasmapheresis and drug immunosuppression on T-cell subsets as defined by monoclonal antibodies

The number of total T-cells and the number of helper/inducer T-cells decreased in 27 of 31 patients with immunologic disorders treated with plasmapheresis and drug immunosuppression. The number of suppressor/cytotoxic T-cells increased in the majority of patients. The helper/inducer to suppressor/cytotoxic cell ratio, which was initially elevated in 26 of 31 patients, decreased significantly in all but 2 patients after therapy. Ten patients were already on drug immunosuppression at the time plasmapheresis was started, and all 10 showed increased helper/inducer to suppressor/cytotoxic cell ratio despite their drug therapy. The helper/inducer to suppressor/cytotoxic cell ratio decreased in all ten patients after plasma exchange. The number and the percentage of total T-cells and helper/inducer cells decreased from prepheresis levels while the number and the percentage of suppressor/cytotoxic cells increased. Plasmapheresis, in combination with drug immunosuppression, was effective in decreasing the elevated helper/inducer to suppressor/cytotoxic cell ratio in disorders of the immune system. In contrast, patients on immunosuppressive drug therapy alone had persistently high immunoregulatory ratio.

Immunopathology of acetylcholine receptors in myasthenia gravis

It is now clear that the muscular weakness and fatigability seen in MG result from an antibody-mediated immune response to AChR. The mechanisms by which antibodies impair transmission are moderately well understood and detection of antibodies in patient's sera is a reliable diagnostic test for the disease. The spectrum of antibody specificities produced in MG is also beginning to be understood, largely through the use of antibodies produced in the experimental model EAMG. Treatment for MG continues to rely heavily on the symptomatic relief afforded by acetylcholinesterase inhibitors. However, the recent recognition of the autoimmune nature of MG has led to increased emphasis on immunosuppression and antibody removal with some beneficial effects. Despite all that has been learned, the level of ignorance has just been pushed back one step--from the neuromuscular junction to the immune system. What initiates the immune response to AChR in MG and how to specifically suppress this aberrant response remain completely unknown.