Anti-acetylcholine receptor Fab fragments isolated from thymus-derived phage display libraries from myasthenia gravis patients reflect predominant specificities in serum and block the action of pathogenic serum antibodies.
Myasthenia gravis (MG) is a prototype antibody-mediated autoimmune disease in which antibodies against nicotinic acetylcholine receptors (AChR) induce loss of functional receptors at the neuromuscular junction. Germinal centers present in MG hyperplastic thymus contain activated B-cells spontaneously producing anti-human AChR (huAChR) Ab in vitro. In order to access the anti-huAChR repertoire phage display Fab libraries of thymic lymphocytes were constructed from two MG patients. A total of four Fabs highly specific for huAChR were isolated that bind to determinants in or near the main immunogenic region (MIR). These anti-huAChR Fabs showed evidence of significant somatic mutations supporting the notion that the anti-huAChR Ab response in MG patients is driven by antigen. A total of two Fabs were able to inhibit up to 90% of donor serum anti-huAChR antibodies. Competition with serum anti-huAChR Ab was also observed in unrelated MG patients and indicate that anti-huAChR Fabs bind to epitopes on huAChR recognized by the majority of MG patients. In vitro antigenic modulation studies demonstrated that anti-huAChR Fabs were able to induce AChR loss when cross-linked by an anti-Fab antibody but not as monovalent Fab. Moreover, anti-huAChR Fabs were able to protect against AChR loss by antigenic modulation induced by MG serum antibodies suggesting a potential therapeutic role for these recombinant Fabs in patients with a myasthenic crisis.
Graus
Y F
YF
Scripps Research Institute, Department of Immunology, La Jolla, CA 92037, USA.
de Baets
M H
MH
van Breda Vriesman
P J
PJ
Burton
D R
DR
D000918:Antibody Specificity / Q000276:immunology; D000941:Antigens / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology; D001435:Bacteriophages; D005822:Genetic Vectors; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology* / Q000302:isolation & purification; D009157:Myasthenia Gravis / Q000276:immunology*; D019151:Peptide Library; D011978:Receptors, Nicotinic / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology / Q000276:immunology
D000941:Antigens; D007140:Immunoglobulin Fab Fragments; D019151:Peptide Library; D011978:Receptors, Nicotinic