Background Anti-Ro52 antibodies are detected in patients with Sjogren's syndrome (SjS), systemic sclerosis (SSc) and other autoimmune rheumatic diseases. Epitope mapping studies of anti-Ro52 in autoimmune rheumatic diseases have failed to find any difference on epitope recognition suggesting a common stimulus for the loss of tolerance to Ro52. Such epitope differences, however, were noted between SjS and non-rheumatic diseases and in particular, SjS-associated primary biliary cirrhosis (SjS-PBC) or PBC alone (1).
Objectives To assess whether or not the Ro52 epitope profile in anti-Ro52+ SSc patients differs from that of SSc-associated PBC (SSc-PBC) or PBC.
Methods Serum samples were obtained from 63 anti-Ro52-positive (by ELISA) patients (33 SSc, 10 SSc-PBC, 20 PBC alone). Antibody reactivity to full length recombinant Ro52 and 5 baculovirus expressed Ro52 fragments spanning the whole sequence [Ro52–1 (aa 1–129), Ro52–2 (aa 125–268), Ro52–3 (aa 269–475), Ro52–4 (aa 57–180, partly overlapping with Ro52–1 and Ro52–2), and Ro52–5 (aa 181–320, partly overlapping with Ro52–2 and Ro52–3)] were tested by a line immunoassay.
Results Reactivity was present to: full length Ro52 in all anti-Ro52 positive SSc, PBC-SSc, or PBC patients by line immunoassay; Ro52–1 in 6/33 (18.2%) SSc, 3/10 (30%) SSc-PBC, and 3/20 (15%) PBC; Ro52–2 in 33/33 (100%) SSc, 10/10 (100%) SSc-PBC and 20/20 (100%) PBC; Ro52–3 in 0/33 (0%) SSc, 0/10 (0%) SSc-PBC and 0/20 (0%) PBC; Ro52–4 in 4/33 (12.1%) SSc, 2/10 (20%) SSc-PBC, and 4/20 (20%) PBC and Ro52–5 in 11/33 (33.3%) SSc 4/10 (40%) SSc-PBC, and 9/20 (45%) PBC respectively (p>0.05 for all epitopes amongst the 3 cohorts). No statistically significant correlation was found.
Conclusions The major epitope of anti-Ro52 does not differ among SSc, PBC-SSc and PBC and is localized on aa125–268, the major epitopic region of anti-Ro52 antibodies in SjS and other rheumatic diseases. Our epitope mapping data suggest that the mechanisms responsible for the loss of tolerance to Ro52 is common amongst diseases.
Mytilinaiou, Maria G.; Meyer Wolfgang; Komorowski, Lars; Probst, Christian; Davies, Edward T.; Vergani, Diego; Bogdanos, Dimitrios P. B-cell epitope mapping of anti-Ro52 responses in patients with primary biliary cirrhosis., Hepatology, Vol. 52 (4), 2010, 489.
Disclosure of Interest C. Liaskos: None declared, A. Gkoutzourelas: None declared, T. Simopoulou: None declared, E. Marou: None declared, T. Scheper Employee of: Euroimmun AG, W. Meyer Employee of: Euroimmun AG, L. Sakkas: None declared, D. Bogdanos: None declared