Responses in vitro of peripheral blood lymphocytes from patients with myasthenia gravis to stimulation with human acetylcholine receptor α-chain peptides: Analysis in relation to age, thymic abnormality, and ethnicity

A Sensitive Method for Detecting Peptide-specific CD4+ T Cell Responses in Peripheral Blood from Patients with Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune neurological disorder typified by skeletal muscle fatigue and most often production of autoantibodies against the nicotinic acetylcholine receptor (AChR). The present study was undertaken to assess the extent of AChR-peptide recognition in MG patients using co-culturing (DC:TC) of autologous monocyte-derived dendritic cells (moDCs) and highly enriched CD4⁺ T cells from the blood as compared to the traditional whole peripheral blood mononuclear cell (PBMC) cultures. We found that the DC:TC cultures were highly superior to the PBMC cultures for detection of reactivity toward HLA-DQ/DR-restricted AChR-peptides. In fact, whereas DC:TC cultures identified recognition in all MG patients the PBMC cultures failed to detect responsiveness in around 40% of the patients. Furthermore, reactivity to multiple peptides was evident in DC:TC cultures, while PBMC cultures mostly exhibited reactivity to a single peptide. No healthy control (HC) CD4⁺ T cells responded to the peptides in either culture system. Interestingly, whereas spontaneous production of IFNγ and IL-17 was observed in the DC:TC cultures from MG patients, recall responses to peptides enhanced IL-10 production in 9/13 MG patients, while little increase in IFNγ and IL-17 was seen. HCs did not produce cytokines to peptide stimulations. We conclude that the DC: TC culture system is significantly more sensitive and better identifies the extent of responsiveness in MG patients to AChR-peptides than traditional PBMC cultures.

Subtle differences in HLA DQ haplotype-associated presentation of AChR α-chain peptides may suffice to mediate myasthenia gravis

The HLA DQA1 and DQB1 alleles were determined on a set of 24 myasthenia gravis patients that had previously been examined for their T-cell proliferative responses to the 18 overlapping peptides representing the extracellular domain of hAChR alpha-chain. Patient responses according to assumed cis or trans haplotypes were significantly higher in most cases relative to normal controls. Comparisons of in vitro peptide-stimulated T-cell responses of patient pairs which had DQA1:DQB1 in common displayed responses in tighter distribution relative to comparisons in which patient pairs did not share the same DQA1:DQB1 haplotype. Similar haplotypes, such as DQA1*0102:DQB1*0602 and DQA1*0102:DQB1*0604, tended to exhibit similar responses and were grouped according to this similarity. Modified F-test and Student's T-test analyses on DQ isoform bearing groups revealed that high responses to peptide alpha34-49 were associated with A1*0102:B1*0602/0604, A1*0301:B1*0302 and A1*0401/0303:B1*0301. Peptide alpha146-162 showed higher responses in A1*0301:B1*0302 group and moderate responses in A1*0401/0303:B1*0301 groups. Differences in the age of disease onset relative to DQ haplotypes were also observed. Groups of A1*0301:B1*0302, A1*0501:B1*0201 and A1*0102:B1*0604 showed earlier ages of disease onset relative to those of A1*0102:B1*0602 or A1*0505:B1*0301.

Down-regulation of T cell responses to AChR and reversal of EAMG manifestations in mice by a dual altered peptide ligand via induction of CD4+CD25+ regulatory cells

A dual altered peptide ligand (APL) composed of the tandemly arranged two single amino acid analogs of two myasthenogenic peptides, p195-212 and p259-271 was demonstrated to down-regulate in vitro and in vivo myasthenia gravis (MG) associated autoreactive responses. In this study, we demonstrate the suppressive properties of the dual APL following immunization with the whole Torpedo AChR (TAChR) and in mice with established experimental autoimmune MG (EAMG). The dual APL acts by up-regulating CD4+ CD25+ cells expressing characteristic regulatory markers along with an associated increase in levels of IL-10 and TGF-beta. The latter cytokine plays a key role in the ameliorating effects of the dual APL.