Autoantibodies to fibroblasts induce a proadhesive and proinflammatory fibroblast phenotype in patients with systemic sclerosis.
OBJECTIVE
Fibroblasts play a major role in the development of systemic sclerosis (SSc), and the occurrence of serum autoantibodies reacting with fibroblast plasma membrane antigens in SSc has been reported. This study was undertaken to investigate whether IgG from SSc sera that react with human fibroblasts modulates the fibroblasts' function.


METHODS
Sera from 69 patients with SSc (28 with limited cutaneous SSc [lcSSc] and 41 with diffuse cutaneous SSc [dcSSc]), 30 patients with sarcoidosis, and 50 matched healthy controls were examined. We evaluated antibody binding to human skin and lung fibroblasts by cell-based enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence, and flow cytometry. We further investigated the ability of purified IgG to modulate 1) intercellular adhesion molecule 1 (ICAM-1) expression, 2) U937 cell adhesion to fibroblasts, and 3) fibroblast steady-state messenger RNA (mRNA) levels of interleukin-1alpha (IL-1alpha), IL-beta, and IL-6, and IL-6 protein production.


RESULTS
Of 69 SSc sera tested by cell-based ELISA, 58% bound to normal skin and lung fibroblasts. The prevalence of binding was significantly higher in dcSSc than in lcSSc (P < 0.05). Only IgG from SSc sera that were positive for antifibroblast antibody (AFA) induced a dose-dependent up-regulation of ICAM-1 expression and IL-6 production, enhancement of U937 cell adhesion, and increased levels of IL-1alpha, IL-1beta, and IL-6 mRNA in fibroblasts. Up-regulation of ICAM-1 mediated by AFA IgG was inhibited by the addition of IL-1 receptor antagonist, indicating an autocrine activation loop.


CONCLUSIONS
Our findings confirm the presence of AFAs in SSc sera and demonstrate, for the first time, that autoantibodies reacting with fibroblast surface molecules act as an extrinsic stimulus inducing fibroblast activation in vitro.
Chizzolini
Carlo
C
Geneva University Hospital, Geneva, Switzerland.
Raschi
Elena
E
Rezzonico
Roger
R
Testoni
Cinzia
C
Mallone
Roberto
R
Gabrielli
Armando
A
Facchini
Andrea
A
Del Papa
Nicoletta
N
Borghi
Maria Orietta
MO
Dayer
Jean Michel
JM
Meroni
Pier Luigi
PL
D000328:Adult; D000368:Aged; D018501:Antirheumatic Agents / Q000494:pharmacology; D001323:Autoantibodies / Q000276:immunology* / Q000494:pharmacology; D002448:Cell Adhesion / Q000276:immunology; D002478:Cells, Cultured; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000276:immunology*; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology / Q000494:pharmacology; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000235:genetics / Q000276:immunology; D015850:Interleukin-6 / Q000235:genetics / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D012595:Scleroderma, Systemic / Q000453:epidemiology / Q000276:immunology*; D016036:Seroepidemiologic Studies; D012795:Sialoglycoproteins / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology
D018501:Antirheumatic Agents; D001323:Autoantibodies; C507763:IL1RN protein, human; D007074:Immunoglobulin G; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D015850:Interleukin-6; D012333:RNA, Messenger; D012795:Sialoglycoproteins; D018799:Intercellular Adhesion Molecule-1