Anti-argonaute2 (Ago2/Su) and -Ro antibodies identified by immunoprecipitation in primary anti-phospholipid syndrome (PAPS).
OBJECTIVE
Primary anti-phospholipid syndrome (PAPS) is an autoimmune condition defined by anti-phospholipid antibodies (aPL) and thrombotic or obstetric events. Some PAPS can evolve into systemic lupus erythematosus (SLE) during follow-up. Few studies systematically examined lupus autoantibodies and their clinical significance in PAPS. The aim of our study is to analyze the clinical and laboratory correlations with lupus-related autoantibodies, detected by immunoprecipitation (IP), a technique not yet systematically applied to investigate autoantibodies in this condition.


METHODS
Sera from 52 PAPS patients were screened by indirect immunofluorescence (IIF) antinuclear antibodies (ANA), IP of ³⁵S-labeled K562 cell extract, and ELISA [anti-Argonaute2 (Ago2, Su), 60kRo, 52kRo, La, dsDNA)]. Anti-Ago2/Su positive sera were also tested for anti-GW bodies (GWBs) by IIF double staining, using rabbit anti-Rck/p54 serum.


RESULTS
First, 56% of PAPS patients (29/52) were ANA positive, mainly with speckled pattern. Anti-Ago2/Su antibodies were found in 13% (7/52), anti-Ro/SSA in 10% (5/52), anti-La in one case. The clinical profile of patients did not seem to be related to the presence of these antibody specificities. However, levels of IgG anti-β2 glycoprotein I antibodies were lower in anti-Ago2/Su positive patients (p = 0.02). None of anti-Ago2/Su or -Ro patients developed SLE during a 2-year follow-up. Ago2 is a key component of GWBs, however, only 1/7 anti-Ago2/Su serum showed a typical cytoplasmic GWBs staining.


CONCLUSIONS
Anti-Ago2/Su and -Ro antibodies are the two autoantibodies detected by IP in our PAPS cohort. Clarifying why Ago2/Su and Ro are specific targets of autoimmunity may help to understand the mechanisms of autoantibody production.
Ceribelli
Angela
A
Rheumatology Unit and Chair, A.O. Spedali Civili di Brescia, Università degli Studi di Brescia, Italy. dott.ceribelli@libero.it
Tincani
Angela
A
Cavazzana
Ilaria
I
Franceschini
Franco
F
Cattaneo
Roberto
R
Pauley
Brad A
BA
Chan
Jason Y F
JY
Chan
Edward K L
EK
Satoh
Minoru
M
D000328:Adult; D000818:Animals; D017152:Antibodies, Antiphospholipid / Q000097:blood / Q000276:immunology; D000918:Antibody Specificity; D016736:Antiphospholipid Syndrome / Q000175:diagnosis / Q000276:immunology*; D060565:Argonaute Proteins; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D004285:Dogs; D004797:Enzyme-Linked Immunosorbent Assay; D015852:Eukaryotic Initiation Factor-2 / Q000276:immunology*; D005260:Female; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods*; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D008297:Male; D051379:Mice; D008875:Middle Aged; D011817:Rabbits; D012261:Ribonucleoproteins / Q000276:immunology*; D055815:Young Adult; D000099207:SS-A Antigen
D017152:Antibodies, Antiphospholipid; D060565:Argonaute Proteins; D001323:Autoantibodies; D015852:Eukaryotic Initiation Factor-2; D012261:Ribonucleoproteins; D000099207:SS-A Antigen; C466422:AGO2 protein, human