title: Autoantibody-mediated regulation of B cell responses by functional anti-CD22 autoantibodies in patients with systemic sclerosis.
abstract: Studies have demonstrated that B cells play important roles in systemic sclerosis (SSc), especially through the CD19/CD22 autoimmune loop. CD22 is a B cell-specific inhibitory receptor that dampens B cell antigen receptor (BCR) signalling via tyrosine phosphorylation-dependent mechanism. In this study, we examined the presence and functional property of circulating autoantibodies reacting with CD22 in systemic sclerosis. Serum samples from 10 tight skin (TSK/+) mice and 50 SSc patients were assessed for anti-CD22 autoantibodies by enzyme-linked immunosorbent assays using recombinant mouse or human CD22. The association between anti-CD22 antibodies and clinical features was also investigated in SSc patients. Furthermore, the influence of SSc serum including anti-CD22 autoantibodies for CD22 tyrosine phosphorylation was examined by Western blotting using phosphotyrosine-specific antibodies reacting with four major tyrosine motifs of CD22 cytoplasmic domain. Anti-CD22 autoantibodies were positive in 80% of TSK/+ mice and in 22% of SSc patients. Patients positive for anti-CD22 antibodies showed significantly higher modified Rodnan skin thickness score compared with patients negative for anti-CD22 antibodies. Furthermore, anti-CD22 antibodies from patients' sera were capable of reducing phosphorylation of all four CD22 tyrosine motifs, while sera negative for anti-CD22 antibodies did not affect CD22 phosphorylation. Thus, a subset of SSc patients possessed autoantibodies reacting with a major inhibitory B cell response regulator, CD22. Because these antibodies can interfere CD22-mediated suppression onto B cell activation in vitro, SSc B cells produce functional autoantibodies that can enhance their own activation. This unique regulation may contribute to the autoimmune aspect of SSc.
authors.affiliation: Department of Dermatology, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Odaka
authors.forename: M
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Y
authors.initials: Y
authors.lastname: Hamaguchi
authors.forename: N
authors.initials: N
authors.lastname: Ishiura
authors.forename: S
authors.initials: S
authors.lastname: Kumada
authors.forename: T
authors.initials: T
authors.lastname: Matsushita
authors.forename: K
authors.initials: K
authors.lastname: Komura
authors.forename: S
authors.initials: S
authors.lastname: Sato
authors.forename: K
authors.initials: K
authors.lastname: Takehara
authors.forename: M
authors.initials: M
authors.lastname: Fujimoto
mesh_terms: D000328:Adult; D000818:Animals; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008875:Middle Aged; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D012595:Scleroderma, Systemic / Q000097:blood / Q000276:immunology* / Q000473:pathology; D051918:Sialic Acid Binding Ig-like Lectin 2 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D001323:Autoantibodies; D051918:Sialic Acid Binding Ig-like Lectin 2; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C080813:emt protein-tyrosine kinase