IgG anti-pentraxin 3 antibodies in systemic lupus erythematosus.
OBJECTIVE
To evaluate the prevalence and correlates of anti-pentraxin 3 (PTX3) antibodies in systemic lupus erythematosus (SLE).


METHODS
Serum samples from 130 patients with SLE, 130 age- and sex-matched healthy subjects and 130 patients with other autoimmune rheumatic diseases (oARD) were analysed by home-made ELISAs using as substrate human recombinant PTX3 and two peptides, PTX3_1 and PTX3_2, obtained from the complete protein, identified as potential antigenic sites using the Lasergene DNA program (DNA Star). Inhibition tests were performed to evaluate potential interferences between bovine serum albumin or C-reactive protein and anti-PTX3 or anti-PTX3 peptides, and between antigens and antibodies. Statistical analysis was performed using receiving operating characteristics curves, the Fisher exact test, two-tailed t test and Pearson correlations.


RESULTS
Patients with SLE had higher levels and prevalence of anti-PTX3, anti-PTX3_1 and anti-PTX3_2 antibodies than patients with oARD or healthy controls (p<0.001 for all). No differences were observed between patients with oARD and healthy controls. A correlation was found between anti-PTX3 and anti-PTX3_2 antibodies (r=0.615, p<0.001). No association was observed between these antibodies and disease activity. Univariate and multivariate analyses showed that anti-PTX3 and anti-PTX3_2 antibody levels and prevalence were higher in patients without glomerulonephritis and in patients positive for antiphospholipid antibody. All inhibition tests were negative apart from PTX3 against anti-PTX3 antibody or, to a lesser extent, against anti-PTX3_2 antibody, and PTX3_2 against anti-PTX3_2 antibody, all in a dose-dependent manner.


CONCLUSIONS
Anti-PTX3 antibodies are significantly prevalent in patients with SLE where they might provide protection from renal involvement. The antigenic properties of PTX3_2 peptide are similar to those of PTX3, suggesting its potential use in further analyses.
Bassi
N
N
Division of Rheumatology, University of Padova, Via Giustiniani 2, Padua, Italy. adoria@unipd.it
Ghirardello
A
A
Blank
M
M
Zampieri
S
S
Sarzi-Puttini
P
P
Mantovani
A
A
Shoenfeld
Y
Y
Doria
A
A
D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D001327:Autoimmune Diseases / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000276:immunology*; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D012216:Rheumatic Diseases / Q000276:immunology; D000683:Serum Amyloid P-Component / Q000276:immunology*; D055815:Young Adult; D000099153:Pentraxins
D001323:Autoantibodies; D015415:Biomarkers; D002097:C-Reactive Protein; D007074:Immunoglobulin G; D000683:Serum Amyloid P-Component; D000099153:Pentraxins