Novel autoantibodies to pituitary gland specific factor 1a in patients with rheumatoid arthritis.
OBJECTIVE
We recently identified a new protein, pituitary gland specific factor 1a (PGSF1a), that is specifically transcribed in the pituitary gland. In our investigation of anti-PGSF1a antibody for pituitary diseases, we examined it in patients with RA and other autoimmune diseases. We unexpectedly discovered the frequent existence of anti-PGSF1a antibody in patients with RA. We therefore examined the prevalence of this antibody to understand its clinical significance in RA.


METHODS
Anti-PGSF1a antibody was detected by radioligand assay using recombinant (35)S-labelled PGSF1a protein. Antibody activity is expressed as an index that was obtained by comparison with normal pooled serum.


RESULTS
RA patients had a significantly higher mean anti-PGSF1a antibody index (n=46, 1.28+/-0.38, P < 0.001) than healthy controls (n=36, 1.04+/-0.13). Indices greater than the cut-off value (mean+2 S.D. of healthy controls) were found in 43.5% (20/46) and 10.0% (2/20) of patients with RA and osteoarthritis, respectively. There was no correlation between the activities of anti-PGSF1a antibodies and titres of rheumatoid factor (RF) or serum C-reactive protein concentrations, but RA patients with more erosive disease had a higher mean anti-PGSF1a antibody index. Four of eight sera samples obtained from RF-negative RA patients were positive for anti-PGSF1a antibodies.


CONCLUSIONS
Anti-PGSF1a antibody is a useful new marker for the diagnosis of RA, especially for RF-negative RA, and may relate to clinical manifestations of RA.
Tanaka
S
S
Department of Laboratory Medicine (D2), Osaka University Graduate School of Medicine, Japan.
Tatsumi
K
K
Tomita
T
T
Kimura
M
M
Takano
T
T
Yoshikawa
H
H
Amino
N
N
D000595:Amino Acid Sequence; D001172:Arthritis, Rheumatoid / Q000175:diagnosis / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood*; D001327:Autoimmune Diseases / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis; D006684:HLA-DR Antigens / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D010003:Osteoarthritis / Q000276:immunology; D011506:Proteins / Q000032:analysis* / Q000235:genetics; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D011869:Radioligand Assay; D012217:Rheumatoid Factor / Q000097:blood; D012680:Sensitivity and Specificity; D017386:Sequence Homology, Amino Acid; D012720:Severity of Illness Index
D001323:Autoantibodies; D015415:Biomarkers; D006684:HLA-DR Antigens; C470507:MIR7-3HG long non-coding RNA, human; D011506:Proteins; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D002097:C-Reactive Protein; D012217:Rheumatoid Factor