Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement

The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.


Anti-Topoisomerase I Antibody Develops Simultaneously with Clinical Onset of Systemic Sclerosis through De Novo T Cell-Dependent Process

Kuwana1,  Masataka, Kaburaki2,  Junichi

Keio University School of Medicine, Tokyo, Japan
Shin-akasaka Clinic, Tokyo, Japan

Purpose:

Anti-topoisomerase I (topo I) antibody is highly specific to patients with systemic sclerosis (SSc), but underlying mechanisms that elicits this autoantibody response still remain unclear. In this study, we have investigated when and how anti-topo I antibody response emerges using blood samples obtained before and after SSc becomes clinically evident.

Method:

Eight patients were selected from 98 patients with diffuse cutaneous SSc and anti-topo I antibody in our database, based on availability of serial serum samples including those obtained before onset of first non-Raynaud's phenomenon manifestation of SSc. Autoantibody assays were performed by indirect immunofluorescence and immunoprecipitation (IP) assay using radio-labeled cellular extracts. Levels, isotype distribution (IgG/IgM), and epitope reactivities of anti-topo I antibodies were evaluated by enzyme-linked immunosorbent assay using recombinant topo I fragments as antigen sources. In some instances, topo I-reactive T cells in circulation were quantified by limiting dilution of sorted peripheral blood CD4+ T cells followed by evaluation of a topo I-specific T cell response.

Results:

A total of 12 sera obtained at a mean of 33.8 months (range 3–70) before SSc onset were available from 8 patients. All sera showed a positive anti-nuclear antibody at a titer ranging from 1:40 to 1:2560, but none of them was positive for anti-topo I despite use of highly sensitive IP assay. In contrast, anti-topo I was detected in all patients at SSc diagnosis, which was made a mean of 8.6 months (range 1–18) after the onset of first non-Raynaud's symptom. Anti-topo I isotype distribution was further evaluated serially in 2 cases in whom diagnosis of SSc was made within 3 months of the onset. In case #324, IgM anti-topo I alone was weakly positive one month after she noticed puffy fingers, although sera obtained at 3 and 50 months earlier were negative for anti-topo I. Three months later, skin thickness and interstitial lung disease became apparent with a prominent increase in IgG anti-topo I (isotype-switch). In case #336, IgM and IgG anti-topo I were positive three months after onset of puffy fingers despite the absence at 14, 38, and 48 months earlier. IgM anti-topo I became undetectable in one year, but IgG anti-topo I level increased and remained high with prominent expansion of topo I-reactive CD4+ T cells in circulation. Serial analysis of reactivities to epitopes on topo I revealed acquisition of IgG reactivity to previously unrecognized epitopes within one year after the onset (epitope-spreading).

Conclusion:

Unlike lupus autoantibodies, development of anti-topo I antibody and clinical onset of SSc are concurrent events in patients with diffuse cutaneous SSc, although positive antinuclear antibody test precedes many years before onset of the disease. In addition, emergence of the anti-topo I antibody response follows a stepwise process of de novo T cell-dependent humoral immune response: production of IgM antibody followed by isotype-switch and epitope-spreading.

To cite this abstract, please use the following information:
Kuwana, Masataka, Kaburaki, Junichi; Anti-Topoisomerase I Antibody Develops Simultaneously with Clinical Onset of Systemic Sclerosis through De Novo T Cell-Dependent Process [abstract]. Arthritis Rheum 2009;60 Suppl 10 :444
DOI: 10.1002/art.25526

Abstract Supplement

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