Molecular analysis of the human autoantibody response to alpha-fodrin in Sjögren's syndrome reveals novel apoptosis-induced specificity.
Lymphocyte infiltration of salivary and lacrimal glands leading to diminished secretion and gland destruction as a result of apoptosis is thought to be pivotal in the pathogenesis of Sjögren's syndrome (SS). The cytoskeletal protein alpha-fodrin is cleaved during this apoptotic process, and a strong antibody (Ab) response is elicited to a 120-kd fragment of cleaved alpha-fodrin in the majority of SS patients, but generally not in other diseases in which apoptosis also occurs. Little is known about the anti-alpha-fodrin autoantibody response on a molecular level. To address this issue, IgG phage display libraries were generated from the bone marrow of two SS donors and a panel of anti-alpha-fodrin IgGs was isolated by selection on alpha-fodrin immunoblots. All of the human monoclonal Abs (hmAbs) reacted with a 150-kd fragment and not with the 120-kd fragment or intact alpha-fodrin, indicating that the epitope recognized became exposed after alpha-fodrin cleavage. Analysis of a large panel of SS patients (defined by the strict San Diego diagnostic criteria) showed that 25% of SS sera exhibited this 150-kd alpha-fodrin specificity. The hmAbs stained human cultured salivary acinar cells and the staining was redistributed to surface blebs during apoptosis. They also stained inflamed acinar/ductal epithelial cells in SS salivary tissue biopsies, and only partially co-localized with monoclonal Abs recognizing the full-length alpha-fodrin. Our study shows that in SS patients, neoepitopes on the 150-kd cleaved product of alpha-fodrin become exposed to the immune system, frequently eliciting anti-150-kd alpha-fodrin Abs in addition to the previously reported anti-120-kd Abs. The anti-150-kd alpha-fodrin hmAbs may serve as valuable reagents for the study of SS pathogenesis and diagnostic analyses of SS salivary gland tissue.
Maruyama
Toshiaki
T
Department of Immunology, The Scripps Research Institute, La Jolla, California, USA.
Saito
Ichiro
I
Hayashi
Yoshio
Y
Kompfner
Elizabeth
E
Fox
Robert I
RI
Burton
Dennis R
DR
Ditzel
Henrik J
HJ
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D001706:Biopsy; D015153:Blotting, Western; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002478:Cells, Cultured; D000939:Epitopes; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D051379:Mice; D008840:Microfilament Proteins / Q000302:isolation & purification / Q000378:metabolism*; D018613:Microscopy, Confocal; D008970:Molecular Weight; D019151:Peptide Library; D012469:Salivary Glands / Q000166:cytology / Q000276:immunology; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D012859:Sjogren's Syndrome / Q000097:blood* / Q000175:diagnosis / Q000276:immunology*; D013347:Subcellular Fractions / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D013049:Spectrin
D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D002352:Carrier Proteins; D000939:Epitopes; D007074:Immunoglobulin G; D008840:Microfilament Proteins; D019151:Peptide Library; D014409:Tumor Necrosis Factor-alpha; D013049:Spectrin