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Residues Within the Alpha Subunit Sequence 304-322 of Muscle Acetylcholine Receptor Forming Autoimmune CD4+ Epitopes in BALB/c Mice

Overview
Journal Immunology
Date 1994 May 1
PMID 7519170
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Abstract

BALB/c mice develop myasthenic symptoms after immunization with rodent acetylcholine receptor (AChR). After immunization with Torpedo AChR (TAChR), their CD4+ cells become strongly sensitized against a conserved region of the TAChR alpha subunit sequence (residues alpha 304-322), and cross-react vigorously with the homologous sequences of mouse and human AChR, which are almost identical. Therefore AChR-specific potentially autoreactive CD4+ cells exist in this strain. We immunized BALB/c mice with the synthetic TAChR sequence alpha 304-322. The CD4+ cells thus sensitized responded to TAChR, indicating that they recognize an epitope(s) produced upon TAChR processing. They recognized peptide alpha 304-322 in association with the I-Ad molecule. Anti-alpha 304-322 CD4+ cells cross-reacted well with the corresponding murine and human synthetic sequences. To identify residues involved in formation of an autoimmune epitope(s), CD4+ cells from mice immunized with peptide alpha 304-322 were challenged in vitro with single residue glycine-substituted analogues of this sequence. Substitution of residue W311, and of any residue within the sequence alpha 313-319 (RKVFIDT), consistently and, in some cases, strongly affected the CD4+ cells response. Substitution of residues in the region alpha 311-319 had variable effects in different experiments, and in general affected moderately the CD4+ response. These results suggest that anti-alpha 304-322 CD4+ cells comprise several clones, recognizing overlapping epitopes which share residues alpha 311-319. The importance of the sequence region alpha 311-319 for formation of CD4+ cell epitope(s) was verified by testing CD4+ cells sensitized to T alpha 304-322 with analogues of this sequence, carrying non-conservative substitutions at positions Q310, K314 and D318. Substitution of Q310 had minimal or no effects, while those of K314 or D318 strongly affected the CD4+ cell response.

References
1.
Schmidt J, RAFTERY M . A simple assay for the study of solubilized acetylcholine receptors. Anal Biochem. 1973; 52(2):349-54. DOI: 10.1016/0003-2697(73)90036-5. View

2.
Bellone M, Ostlie N, Karachunski P, Manfredi A . Cryptic epitopes on the nicotinic acetylcholine receptor are recognized by autoreactive CD4+ cells. J Immunol. 1993; 151(2):1025-38. View

3.
Elliott J, Dunn S, Blanchard S, RAFTERY M . Specific binding of perhydrohistrionicotoxin to Torpedo acetylcholine receptor. Proc Natl Acad Sci U S A. 1979; 76(6):2576-9. PMC: 383650. DOI: 10.1073/pnas.76.6.2576. View

4.
Christadoss P, Lennon V, Krco C, LAMBERT E, David C . Genetic control of autoimmunity to acetylcholine receptors: role of Ia molecules. Ann N Y Acad Sci. 1981; 377:258-77. DOI: 10.1111/j.1749-6632.1981.tb33737.x. View

5.
Christadoss P, Lindstrom J, Talal N . Cellular immune response to acetylcholine receptors in murine experimental autoimmune myasthenia gravis: inhibition with monoclonal anti-I-A antibodies. Cell Immunol. 1983; 81(1):1-8. DOI: 10.1016/0008-8749(83)90205-8. View