Anti-PDGFR-alpha antibodies measured by non-bioactivity assays are not specific for systemic sclerosis.
OBJECTIVE
To evaluate the presence of anti-PDGFR-alpha antibodies by immunological methods in patients with systemic sclerosis (SSc).


METHODS
Fifty-eight women diagnosed with SSc and 36 healthy women controls were included. IgG anti-PDGFR-alpha were measured by ELISA and immunoblot. Associations with clinical and immunological findings were also studied.


RESULTS
Non-significant differences were detected between patients with SSc and controls: median value 0.287 (range 0-2.06) versus median value 0.226 (range 0-2.94), respectively (p = 0.583). No correlation between the presence of anti-PDGFR-alpha antibodies and clinical and serological features was found. Serum samples from patients with SSc and healthy people who had high titres of anti-PDGFR-alpha antibodies by ELISA recognised the same band corresponding to PDGFR-alpha by immunoblot.


CONCLUSIONS
Although anti-PDGFR-alpha antibodies seem to be disease-specific when determined by bioactivity assays, these antibodies are also detected in normal subjects when immunological methods are used. Thus, anti-PDGFR-alpha antibodies may arise from natural autoantibodies. Possibly, SSc autoantibodies recognise a different epitope on the PDGFR-alpha molecule which triggers its stimulatory effect when analysed by functional assays. Alternatively, naturally occurring autoantibodies may even become pathogenic after affinity maturation and class switching in genetically susceptible subjects.
Balada
E
E
Research Unit in Systemic Autoimmune Diseases, Vall d'Hebron Research Institute, Hospital Vall d'Hebron, Barcelona, Spain.
Simeón-Aznar
C P
CP
Ordi-Ros
J
J
Rosa-Leyva
M
M
Selva-O'Callaghan
A
A
Pardos-Gea
J
J
Fonollosa-Pla
V
V
Vilardell-Tarrés
M
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006801:Humans; D008875:Middle Aged; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000276:immunology*; D012595:Scleroderma, Systemic / Q000276:immunology*; D012680:Sensitivity and Specificity
D001323:Autoantibodies; D015415:Biomarkers; D020796:Receptor, Platelet-Derived Growth Factor alpha