The B-cell repertoire in myasthenia gravis includes all four acetylcholine receptor subunits

By enumerating cells secreting IgG antibodies of particular specificities using an enzyme-linked immunospot (ELISPOT) assay, the B-cell responses to Torpedo acetylcholine receptor (AChR) and its α-, β-, γ- and δ-subunits in peripheral blood from patients with myasthenia gravis (MG), and controls with other neurological diseases (OND) as well as healthy subjects were determined. Compared to controls, the patients with MG had elevated numbers of B cells secreting antibodies against AChR and its α-, β-, γ- and δ-subunits in peripheral blood in parallel. The mean numbers of anti-AChR antibody secreting cells were about 17 per 10⁵ blood MNC, and for the subunits 10 to 15 in MG patients, compared to between 0.8 and 1.9 per 10⁵ blood MNC in OND patients, and 0.1 to 0.3 in healthy controls. Such B cells detected in controls probably represent naturally occurring B cells responded to AChR and its subunits. The finding that most (60%) MG patients had B cells predominantly recognizing the α-subunit may be an indirect argument for the existence of a main immunogenic region (MIR). In the remaining 40% of patients with MG the predominant B-cell responses were directed to β-, γ- or δ-subunit. The data suggest that all four AChR subunits may function as strong immunogens in MG, though the α-subunit may be the major immune target in a substantial proportion of MG patients.     

重症肌无力患者对糖皮质激素的敏感性与糖皮质激素受体的关系

目的　了解重症肌无力(MG)患者对糖皮质激素(GC)敏感性与糖皮质激素受体(GR)的关系。 方法　观察10例MG患者及10名健康对照。采用 3　H-地塞米松( 3　H-DEX)放射配体法测定外周血单个核细胞(PBMC)GR。分别用植物血凝素(PHA)、髓鞘碱性蛋白(MBP)、乙酰胆碱受体(AChR)刺激PBMC， 3　H-TdR掺入法检测体外淋巴细胞增殖反应，地塞米松(DEX)抑制淋巴细胞增殖反应。 结果　正常对照及MG患者PBMC对PHA及MBP刺激的增殖反应差别不显著(P>,0 .05)。而MG患者PBMC对AChR的反应明显高于正常对照者(P<,0 .01)。DEX对MG患者PBMC特异性增殖反应的抑制率为42 .14%, 而对正常对照PBMC的增殖反应的抑制率为21 .62％，两组间有很显著区别(P<,0 .01)。GR数与DEX抑制率间有很良好的相关关系(r=0 .943, P<,0 .01)。 结论　MG PBMC GR数与体外DEX对PBMC 特异性增殖反应的抑制效应有良好的一致性。DEX对抗原特异性淋巴细胞增殖反应的抑制性可作为了解MG患者对GC敏感性的一项指标。     

Myasthenia gravis: T and B cell reactivities to the beta-bungarotoxin binding protein presynaptic membrane receptor.

Antibodies against acetylcholine receptor (AChR) can be detected in most patients with myasthenia gravis (MG) and are considered to be involved in the immunopathogenesis of this disease. AChR are isolated from crude receptor preparations by binding to alpha-bungarotoxin (alpha-BuTx). Patients with MG have also antibodies against a second protein tentatively named presynaptic membrane receptor (PsmR), which has been isolated from crude receptor utilizing beta-bungarotoxin (beta-BuTx). PsmR could represent another antigen besides AChR relevant for the development of MG. We have now evaluated the T cell reactivity to PsmR in MG and controls by analysing the frequencies of cells which in response to PsmR in short-term cultures secreted interferon-gamma (IFN-gamma). The B cell response to PsmR was analysed in parallel by counting cells secreting anti-PsmR antibodies. Most patients with MG had PsmR reactive T cell in blood with a median number of about 1 per 44,000 mononuclear cells. Cells secreting anti-PsmR antibodies belonging to the IgG and IgA isotypes, less frequently of the IgM isotype were detected in most MG patients. A positive correlation was found between T cells reactive with PsmR and anti-PsmR IgG antibody secreting cells. PsmR reactive T and B cells were also detected in control patients, but at much lower numbers. Our results indicate that MG is accompanied by T as well as B cell responses to PsmR, in addition to the previously recognized responses to AChR. It remains to be shown whether these PsmR reactivities are of pathogenetic importance in MG.     

Myasthenic thymus and thymoma are selectively enriched in acetylcholine receptor-reactive T cells

We compared T-cell proliferative responses to acetylcholine receptor (AChR) and to purified protein derivative (PPD) (of tuberculin) of hyperplastic thymus, thymoma, and blood cells from patients with myasthenia gravis (MG). Hyperplastic MG thymus cells gave significantly higher and more consistent responses to AChR than parallel cultures of autologous blood cells, whereas responses to PPD showed an opposite trend. Thus there was a preferential localization of AChR-reactive T cells in the hyperplastic MG thymus. Furthermore, there was a strong correlation between blood and thymus cell responses to PPD (but not to AChR), arguing that the hyperplastic MG thymus contains a sample of sensitized peripheral T cells. By contrast, both AChR- and PPD-responsive T cells were almost undetectable in thymus from nonmyasthenic patients, which is evidently much less receptive to circulating T cells. Cells from MG thymomas showed the highest stimulations by AChR but did not consistently react to PPD. However, the uninvolved thymus adjacent to these thymomas behaved almost identically to the hyperplastic samples described above. Our interpretation is that AChR-specific T cells are initially sensitized in the MG thymoma but are selectively trapped in the hyperplastic thymus after being primed elsewhere.     

Suppression of experimental autoimmune myasthenia gravis by nasal administration of acetylcholine receptor

Experimental autoimmune myasthenia gravis (EAMG) is a well established animal model, which can be induced in various animal species and strains with acetylcholine receptor (AChR) and represents an experimental counterpart of human myasthenia gravis (MG). Current immunotherapies of both EAMG and MG are non-specific and limited by their toxicity. Tolerance to EAMG has been achieved by oral administration of milligram quantities of Torpedo AChR. In the present report we demonstrate that nasal administration of microgram doses of Torpedo AChR to female Lewis rats prior to immunization with Torpedo AChR and complete Freund's adjuvant resulted in the prevention of subsequently induced EAMG, the suppression of serum anti-AChR antibody levels, the decrease of delayed-type hypersensitivity responses to AChR, as well as the suppression of AChR-specific immunoglobulin G-secreting cells, AChR-reactive interferon-γ-secreting cells and T cell proliferation in peripheral lymphoid organs, particularly in popliteal and inguinal lymph nodes regional to immunization. We conclude that clinical signs of EAMG can be efficiently prevented by nasal administration of AChR in parallel with the downregulation of both B and T cell responses specific to AChR.     

重组白细胞介素2及T细胞亚群对重症肌无力患者AChR—ab的影响

对１９例全身型重症肌无力（ＭＧ）患者周围血Ｂ细胞分化能力进行了研究，并观察重组白细胞介素２（ｒＩＬ－２）及Ｔ细胞亚群对其影响。方法分离外周血纯Ｂ细胞，体外与电鳗乙酰胆碱受体（ＡＣｈＲ）一起培养，并分别加入去ＣＤ４＋Ｔ细胞，去ＣＤ８＋Ｔ细胞及ｒＩＬ－２。用酶联免疫－生物素法检测其上清液的乙酰胆碱受体抗体（ＡＣｈＲ－ａｂ）。同时以１０例健康人为对照组。结果去ＣＤ８＋Ｔ细胞后ＡＣｈＲ－ａｂ的产生无明显增加；去ＣＤ４＋Ｔ细胞加入ｒＩＬ－２后ＡＣｈＲ－ａｂ产生减少。结论提示ｒＩＬ－２对ＭＧ患者有潜在治疗价值。     

Presentation of endogenous acetylcholine receptor epitope by an MHC class II-transfected human muscle cell line to a specific CD4 T cell clone from a myasthenia gravis patient

Muscle or thymic myoid cells, if induced to express MHC class II in addition to endogenous acetylcholine receptor (AChR), might present epitopes derived from the AChR to specific CD4⁺ T cells. These T cells could in turn initiate or maintain the anti-AChR response that is responsible for AChR loss in myasthenia gravis (MG). We transfected the AChR⁺ TE671 (rhabdyyosarcomyosarcoma) cells with HLA-DR4 and co-cultured them with the DR4-restricted, CD4⁺ T cell clone (PM-A1; raised from a hyperplastic thymus of an MG patient and previously shown to recognise all forms of the AChR that contain the sequence α144–156). Significant T cell activation, demonstrated both by ³H-thymidine incorporation and by lysis of the TE671 cells, was found in the presence of added α144–156 and, more importantly, in the absence of exogenous antigen. These results show that MHC class II-expressing muscle or other AChR-expressing cells could present endogenous AChR to pathogenic T cells. This process may be important in the aetiology of MG.     

重症肌无力胸腺单个核细胞白细胞介素-2、白细胞介素-10及其mRNA水平的变化

目的　研究重症肌无力 ( myasthenia gravis,MG)患者胸腺是否存在辅助性 T细胞 ( Th)亚群的免疫活性紊乱。方法　利用亲和层析法自人腓肠肌纯化获得乙酰胆碱受体 ( ACh R)并进行了鉴定 ,然后用其作为特异性抗原 ,经体外培养刺激 5例 MG患者胸腺和外周血单个核细胞 ,酶联免疫吸附分析 ( ELISA)法检测上清液中白细胞介素 -2 ( IL-2 )、白细胞介素 -1 0 ( IL-1 0 )水平 ,狭缝印迹杂交法检测 MG胸腺及外周血 IL-1 0 m RNA的表达。结果　MG胸腺和外周血经 ACh R刺激后 ,其上清液 IL-2水平略高于对照组 ( P>0 .0 5 ) ,经 ELISA法和狭缝印迹杂交法发现 MG外周血 IL-1 0及其 m RNA表达水平均略高于对照组 ( P>0 .0 5 ) ,胸腺则明显高于对照组( P<0 .0 5 )。结论　 MG发病过程中 IL-1 0的异常增高可能发生于转录或转录以上水平 ,其异常表达的机制有待于进一步研究。     

Clinical significance of neurobiochemical profiles in the lumbar cerebrospinal fluid of Alzheimer’s disease patients

Immunoreactivities of total apolipoprotein E (ApoE-IR), amyloid beta peptide(1-42) (Abeta42-IR), interleukin-6 (IL-6-IR), substance P (SPIR) and total tau protein (TTIR) were measured in lumbar cerebrospinal fluid samples of patients with Alzheimer's disease (AD), non-Alzheimer's dementias (NAD), neurological disorders without cognitive impairment (OND) and controls without central nervous system disease using sensitive and specific enzyme immunoassay methods. TTIR was highly significantly increased (P < 0,001) and Abeta42-IR was significantly decreased (P < 0,001 vs. OND/CO, P < 0,03 vs. NAD) in the AD cohort compared with the other diagnostic groups. Significant increases in AD were also found for ApoE-IR (P < 0,001) and IL-6 (P < 0,03), but there was a considerable overlap between groups. In the total AD cohort, SPIR was not significantly changed, but AD patients with late disease onset (>65 years) showed significantly higher values than both early onset patients (<65 years) and controls (P < 0,05). Discriminant function analysis showed that Abeta42-IR (cut-off value 375pg/ml) and TTIR (cut-off value 440 pg/ml) levels contributed most to the group classification of patients. At 85% sensitivity for AD and 100% specificity for controls, the combined evaluation of Abeta42-IR and TTIR in this cross-sectional study resulted in a graph separating AD from non-AD patients with increased specificity of 91% and 75% for AD versus OND and NAD, respectively.     

Transforming growth factor-β1 suppresses autoantigen-induced expression of pro-inflammatory cytokines but not of interleukin-10 in multiple sclerosis and myasthenia gravis

Multiple sclerosis (MS) is associated with high levels of circulating T lymphocytes that respond to the myelin antigens myelin basic protein (MBP) and proteolipid protein (PLP) by producing various cytokines including interferon-γ (IFN-γ) that makes MS worse and transforming growth factor-β (TGF-β), an endogenously produced immunosuppressant that might act beneficially. To further define the role of TGF-β in MS, we examined the effects of recombinant TGF-β1 (rTGF-β1) on autoantigen-mediated regulation of cytokines in MS and myasthenia gravis (MG). Blood mononuclear cells (MNC) were cultivated with or without rTGF-β1, and with or without autoantigen or the recall antigen PPD. MNC expressing cytokine mRNA were detected after in situ hybridization with radiolabeled cDNA oligonucleotide probes. Femtogram concentrations of rTGF-β1 suppressed MBP-, PLP- and PPD-induced upregulation of IFN-γ, IL-4, IL-6, tumor necrosis factor-α (TNF-α), TNF-α and perforin in MS, and acetylcholine receptor (AChR)-induced augmentation of these pro-inflammatory cytokines in MG, but had no effects on autoantigen- or PPD-induced expression of IL-10 or TGF-β itself. rTGF-β1 also suppressed numbers of myelin antigen-reactive IFN-γ- and IL-4-secreting cells in MS and AChR-reactive IFN-γ and IL-4 secreting cells in MG. The selective suppressive effects of TGF-β1 on autoantigen-induced upregulation of pro-inflammatory cytokines makes TGF-β1 attractive as a treatment alternative in MS and MG.     

The role of complement in myasthenia gravis: serological evidence of complement consumption in vivo

BACKGROUND: Antibodies to the acetylcholine receptor (AChR) titin and the ryanodine receptor (RyR) occur in myasthenia gravis (MG). These antibodies are capable of complement activation in vitro. The involvement of the complement system should cause consumption of complement components such as C3 and C4 in vivo. MATERIALS AND METHODS: Complement components C3 and C4 were assayed in sera from 78 AChR antibody-positive MG patients and 52 healthy controls. Forty-eight of the patient sera contained titin antibodies as well, and 20 were also RyR antibody-positive. RESULTS: MG patients with AChR antibody concentrations above the median (11.2 nmol/l) had significantly lower mean C3 and C4 concentrations in serum compared to those with AChR antibody concentrations below the median. Titin antibody-positive MG patients, titin antibody-negative early-onset MG patients, titin antibody-negative late-onset MG patients, and controls had similar C3 and C4 concentrations. Nor did mean C3 and C4 concentrations differ in MG patients with RyR antibodies. Patients with severe MG (grades 4 and 5) had similar C3 and similar C4 levels compared to those with mild MG (grades 1 and 2). CONCLUSION: An increased in vivo complement consumption was detected in MG patients with high AChR antibody concentrations, unrelated to MG severity and non-AChR muscle antibodies.     

T cell reactivity to P0, P2, PMP-22, and myelin basic protein in patients with Guillain-Barre syndrome and chronic inflammatory demyelinating polyradiculoneuropathy

Objectives: It has been suggested that autoimmunity to peripheral myelin proteins is involved in the pathogenesis of Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We aimed to compare reactivity of peripheral blood mononuclear cells (PBMC) to antigens of peripheral myelin proteins in patients with GBS and patients with CIDP with that of healthy controls and patients with other non-immune mediated neuropathies (ON). Methods: We prepared PBMC from blood from 83 healthy controls and from 64 patients with GBS, 54 with CIDP, and 62 with ON. PBMC were tested in antigen specific proliferation assays against peptides from myelin proteins P0, P2, PMP22, and myelin basic protein (MBP), which is identical to myelin P1, and against whole human MBP. Interferon-gamma (IFN-γ) and interleukin (IL)-5 enzyme linked immunospot (ELISPOT) assays were also performed in some subjects to assess spontaneous and peripheral myelin antigen specific PBMC cytokine secretion. Results: Antigen specific PBMC proliferation assays showed no significant elevation of peptide specific T cell responsiveness in patients with GBS or CIDP compared with healthy controls or patients with ON. Levels of spontaneous ELISPOT IFN-γ secretion were increased in patients with GBS and significantly increased in those with CIDP compared with healthy controls and patients with ON. No convincing differences in antigen specific ELISPOT IFN-γ secretion levels to individual peptides were detectable in patients with GBS. The proportion of patients with CIDP with an increased number of PBMC producing IFN-γ in response to peptide PMP-22_51–64 was significantly increased compared with healthy controls and patients with ON. No significant differences in antigen specific ELISPOT IL-5 secretion levels were detectable in patients with GBS or CIDP compared with controls, but levels of spontaneous IL-5 secretion were significantly higher in patients with CIDP than in healthy controls or patients with ON. Conclusions: Although the lack of significantly increased antigen specific PBMC proliferation in GBS and CIDP does not support a role for T cells, the more sensitive ELISPOT technique detected increased numbers of PBMC secreting IFN-γ spontaneously in 25% of patients with GBS, providing further evidence for a role of T cells in the immunopathology of GBS. Increased numbers of spontaneous IFN-γ and IL-5 secreting cells, and increased IFN-γ secretion in response to PMP-22_51–64, in patients with CIDP provide further evidence for a role of myelin specific T cells in CIDP.     

Rituximab treatment of myasthenia gravis: A systematic review

Rituximab is a chimeric mouse/human anti‐CD20 monoclonal immunoglobulin. We reviewed the efficacy and safety of rituximab in 169 myasthenia gravis (MG) patients from case reports and series. Antibodies to the acetylcholine receptor (AChR) were present in 59% and muscle‐specific tyrosine kinase (MuSK) in 34%. Modified Myasthenia Gravis Foundation of America postintervention scale of minimal manifestations (MM) or better occurred in 44%, and combined pharmacologic and chronic stable remission in 27% overall; MM or better was achieved in 72% of MuSK MG and 30% of AChR MG (P < 0.001). Posttreatment relapses decreased more in MuSK MG (P = 0.05). Response predictors were MuSK MG, less severe disease, and younger age at treatment. Among a responder subset, 26% of AChR and 82% of MuSK MG patients showed decreased posttreatment antibody titers. Rituximab was generally well tolerated. Detectable serum rituximab and depleted CD20⁺ B‐cells were observed up to 20 and 16 weeks, respectively, after 4 weekly infusions. Muscle Nerve 56 : 185–196, 2017     

亚低温治疗对实验性脑出血大鼠死亡率及脑组织钙含量的影响

目的本研究观察３２℃亚低温对实验性脑出血大鼠２４ｈ内死亡率和脑组织钙含量的影响。方法１３４只大鼠分成两部分：（１）６８只大鼠用于死亡率观察;（２）６６只大鼠用于脑组织钙含量测定。每一部分分成假手术对照组、常温脑出血组及亚低温脑出血组。结果常温组２４ｈ内死亡率为３６．６７％,亚低温组为４．５５％;脑组织钙含量常温组较对照组和亚低温组为高。结论亚低温治疗能显著减少实验性脑出血大鼠２４ｈ内死亡率,减少脑出血后脑组织钙含量。     

Myasthenia in SCID mice grafted with myasthenic patient lymphocytes: role of CD4+ and CD8+ cells

OBJECTIVES: Acetylcholine receptor (AChR)-specific CD4+ cells are present in MG patients, and synthesis of the high-affinity immunoglobulin G (IgG) autoantibodies (autoAb) against the muscle AChR that causes MG symptoms requires intervention of CD4+ cells. The role of CD4+ cells in MG pathogenesis has been postulated but never proven. MG patients do not have anti-AChR cytotoxic phenomena, and it has been assumed that CD8+ cells do not have a pathogenic role in MG. However, CD8+ cells may facilitate rodent experimental MG, raising the possibility that CD8+ cells might be necessary also in MG. In this study we examined whether CD4+ and CD8+ cells play a role in the pathogenesis of MG and whether CD4+ cells specific for AChR epitope sequences recognized by most MG patients ("universal" epitopes) drive the synthesis of pathogenic antibodies. METHODS: First we characterized a chimeric human-mouse model of MG in severe combined immunodeficiency (SCID) mice engrafted with blood lymphocytes (BL) from MG patients. We used that model to determine whether CD4+ and CD8+ cells are necessary for transfer of MG symptoms. We engrafted SCID mice intraperitoneum with BL from 19 MG patients and 5 healthy controls. We engrafted some mice with either BL, BL depleted in CD4+ or CD8+ cells from the same patient, or CD4+ depleted BL reconstituted with CD4+ T cells from the same patient, specific for "universal" AChR epitopes or for two unrelated antigens, tetanus and diphtheria toxoids. We tested the mice for myasthenic symptoms for 7 to 18 weeks. RESULTS: Mice transplanted with BL, or CD8+ depleted BL, or CD4+-depleted BL reconstituted with anti-AChR CD4+ cells from MG patients frequently developed myasthenic weakness. The mice had human anti-AChR Ab in the serum and bound to muscle AChR. Mice transplanted with BL from controls, or CD4+-depleted BL from MG patients, or CD4+-depleted BL from an MG patient reconstituted with CD4+ cells specific for tetanus or diphtheria toxoids did not develop myasthenic weakness or anti-AChR Ab. CONCLUSIONS: CD4+ cells are necessary for MG pathogenesis; CD8+ cells may not be. CD4+ cells specific for "universal" AChR epitopes help the synthesis of pathogenic Ab.     

Apolipoprotein E epsilon 4 is associated with an increased vulnerability to cell death in Alzheimer’s disease

Summary. The presumption to suffer from Alzheimer’s disease (AD) accelerates with aging. One important risk factor seems to be the isoform epsilon 4 of the apolipoprotein E gene (Apo ɛ4), which increases the risk to develop AD at an earlier age. Furthermore, convincing evidence is provided that apoptotic cell death mechanisms play an important role in neuronal cell death in AD. In the present study, we investigated whether abnormalities in apoptosis and caspase-3 activity can be found at the level of lymphocytes and a T cell subtype, CD4 T cells, from AD patients compared to aged sex- and ApoE genotype-matched non-demented controls. Under different experimental conditions (at baseline or after in vitro incubation in the presence of proapoptotic stimuli) increased levels of apoptosis and enhanced caspase-3 activity were detected in lymphocytes from AD patients. This difference was most pronounced in the CD4⁺ T cell subtype. Notably, we found a significant increase of apoptotic cells and caspase-3 activity in lymphocytes from AD patients bearing one or two alleles of the ApoE4 compared to non-E4 carriers. Again, these effects were strongest in CD4⁺ T cells. Circulating amyloid-beta (Aβ) levels did not differ between AD patients bearing ApoE4 and non-ApoE4 and age-matched controls. Therefore, it is likely that circulating Aβ is not responsible for the observed effects, which might rather reflect an ongoing systemic response in AD, e.g. an increase in CD95 expression.     

Th22细胞及相关因子在重症肌无力患者外周血中的表达

目的研究重症肌无力(myasthenia gravis,MG)患者外周血辅助性T细胞22(T helper 22cells,Th22)和白细胞介素-22(interleukin-22,IL-22)的表达以及两者间的相关性。方法收集25例MG患者和24例健康对照者,其中眼肌型重症肌无力(ocular myasthenia gravis,OMG)患者14例,全身型重症肌无力(general myasthenia gravis,GMG)患者11例。采用流式细胞仪检测MG患者和健康对照者外周血单个核细胞(peripheral blood mononuclear cells,PBMC)中Th22细胞的比例,采用酶联免疫吸附实验(enzyme-linked immunosorbent assay,ELISA)检测血浆IL-22的表达。比较各组间Th22细胞比例和IL-22表达水平差异,以及Th22细胞比例和IL-22表达间的相关性。结果 MG患者PBMC中Th22细胞比例、血浆IL-22表达水平均显著低于健康对照组[(0.60±0.07)%比(0.92±0.09)%,P0.01;(18.65±1.38)pg/mL比(24.54±1.85)pg/mL,P0.05];OMG与GMG患者间Th22细胞比例、IL-22表达水平均无统计学差异(均P0.05);MG患者PBMC中Th22细胞比例与IL-22表达水平间呈中度正相关(r=0.59,P0.01)。结论 MG患者体内Th22细胞比例及血浆IL-22表达水平减低可能导致免疫功能紊乱进而影响MG的发病。     

Defective mitogenic responses in myasthenia gravis and multiple sclerosis

Using in vitro lymphocyte proliferation induced by the phytomitogen concanavalin A (ConA), we investigated immune function and regulation in patients with myasthenia gravis (MG) and multiple sclerosis (MS). Unfractionated peripheral blood mononuclear cells of normal individuals responded to a wide range of ConA concentrations; the T cell fraction responded to a lesser degree and only to high concentrations. These findings suggest the presence of two receptors for ConA, one of high affinity present on a non-T cell accessory cell and the other of low affinity present on T cells. Contrasting defects in the level of response of unfractionated lymphocytes and T cells were found in patients with MG and MS. The peak response of T cells in the MG patients was 22.6 ± 9.6 ± 10³ cpm (mean ± SEM) compared with 54.6 ± 6.5 × 10(3) for controls (p < 0.05), while the response of unfractionated lymphocytes did not differ from that in controls. For MS patients, the unfractionated lymphocyte response was diminished: 56.3 ± 2.8 × 10³ cpm versus 70.5 ± 4.5 × 10³ for controls (p < 0.05), while the T cell response was normal. These results indicate a defect in the direct T cell response in MG; in contrast, in MS the response requiring T cell-accessory cell interaction is abnormal.     

Imbalances in T-cell subpopulations in myasthenia gravis

Distributions of peripheral blood lymphocyte subpopulations and T-cell subsets were studied in 38 patients with myasthenia gravis (MG) and 23 healthy controls. T cells were detected by rosette formation with sheep red blood cells and B cells with erythrocyte-antibody-complement (EAC) complexes. Tμ cells were identified by rosette formation of T cells with Ox RBC-IgM complexes, and Tγ cells with Ox RBC-IgG complexes. The means of total lymphocyte count and active T cell percentage were marginally significantly lower in MG patients than in normal controls (0.05 < P < 0.1). The mean percentage of Tμ cells was higher in MG patients than in controls (50.2 ± 11.8% vs. 38.5 ± 15.3%, P < 0.01), whereas that of Tγ cells in the former was lower than that in the latter (20.4 ± 7.1% vs. 27.6 ± 6.2%, P < 0.001). Thus, the loss of regulatory suppressor T cells and the increase of helper T cells in the patients are in favour of regarding MG as an autoimmune disease. The fact that the percentage of Tγ cells was significantly decreased in MG patients after autologus serum incubation, and that no such a phenomenon was seen in normal controls, may suggest a possible role of serum factors in the pathogenesis of MG.     

Synthesis of anti-acetylcholine receptor antibodies by CD5- B cells from peripheral blood of myasthenia gravis patients

An increased frequency of CD5⁺ B cells (or, according to a new nomenclature, B 1 cells) has been detected in the peripheral blood of a proportion of patients with myasthenia gravis (MG), as in some other autoimmune diseases. To elucidate the pathogenic significance of this B-cell subset in myasthenia gravis, mononuclear cells from the peripheral blood of six MG patients were separated into T and B lymphocytes by a magnetic cell separation procedure employing superparamagnetic microbeads (MACS). Subsequently, the B-cell fraction was depleted of CD5⁺ B cells in a second separation. The resulting purified CD5^– B-cell fraction was cultured alone or with the addition of autologous T cells. Anti-acetylcholine receptor (AChR) synthesis by CD5^– B cells in cultures with T cells was significantly increased by pokeweed mitogen (176 ±130 fmol/ml per week/2 × 10⁵ B cells) compared with unfractionated cells (75 ± 101) or CD5^– B cells alone (19 ± 4). These results demonstrate that in MG anti-AChR are synthesized, at least in part, by CD5^– B cells which are dependent on T cells. Although this does not exclude the existence of AChR-specific CD5⁺ B cells, it provides evidence against a pivotal role of this B-cell subset in anti-AChR synthesis.