Prominent T-Cell Responses against the Acetylcholine Receptor ε Subunit in Myasthenia Gravis

Abstract

The human acetylcholine receptor (AChR) is well characterized as the target antigen in myasthenia gravis (MG). Pathogenic antibody responses against the AChR alpha-chain have been investigated extensively and are of diagnostic and prognostic value. However, less is known on the pathogenetic relevance of T-cell responses against epitopes of the different AChR chains (alpha, epsilon, gamma). Using an enzyme-linked immunospot (ELISPOT) assay we measured T-cell responses against recombinant fragments and synthetic peptides of the α and the ε subunits of the human AChR in MG patients (n=15) and in healthy donors (HD; n=9). In MG, highest T-cell responses were noted against recombinantly expressed Epsilon 1-221. Among the synthetic peptides Epsilon 201-215 showed the most prominent T-cell response and represented the peptide with the most remarkable difference between MG and HD. Taken together, prominent T-cell responses against the ε subunit of the human AChR indicate an important role in the pathogenesis of MG.

Figure 1

Frequency of IFN-γ-secreting events per 10⁶ PBL in single donors. ELISPOT assay was performed as described in the text. Results are assigned as the numbers of IFN-γ-secreting events among 10⁶ PBL minus the corresponding numbers of events per 10⁶ PBL without antigen. Negative results (spot number without antigen exceeding spot number with antigen) were defined zero. Grey bars, mean response ± SD; black bars, mean positive response ± SD; crosses, median positive response; MG, myasthenia gravis patients; HD, healthy donors. Note the high standard deviations due to heterogeneous responses of single individuals (see Table 1). Note the different Y axis scales using four different recombinant fragments. (a) fragment Alpha 1-103; (b) Alpha 1-209; (c) Alpha 327-398; (d) Epsilon 1-221.

Figure 2

(a) Mean response, (b) mean positive response, and (c) median response of the numbers of IFN-γ-secreting events among 10⁶ PBL minus the corresponding numbers of events per 10⁶ PBL without antigen. Negative results (spot number without antigen exceeding spot number with antigen) were defined zero. MG, myasthenia gravis patients; HD, healthy donors.