Human autoantibodies to diacyl-phosphatidylethanolamine recognize a specific set of discrete cytoplasmic domains

Authors

  • C. C. F. C. Laurino,

    1. Rheumatology Division, Universidade Federal de São Paulo, Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil,
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  • M. J. Fritzler,

    1. Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada,
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  • R. A. Mortara,

    1. Departamento de Microbiologia, Imunologia e Parasitologia, UNIFESP-EPM, São Paulo, Brazil,
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  • N. P. Silva,

    1. Rheumatology Division, Universidade Federal de São Paulo, Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil,
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  • I. C. Almeida,

    1. Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, TX, USA, and
    2. Departamento de Parasitologia, ICB, Universidade de São Paulo, São Paulo, Brazil
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  • L. E. C. Andrade

    Corresponding author
    1. Rheumatology Division, Universidade Federal de São Paulo, Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil,
      Dr Luís E. C. Andrade, Rheumatology Division, Universidade Federal de São Paulo (UNIFESP), Rua Botucatu 740, São Paulo, SP 04023–062, Brazil.
      E-mail: luis@reumato.epm.br
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Dr Luís E. C. Andrade, Rheumatology Division, Universidade Federal de São Paulo (UNIFESP), Rua Botucatu 740, São Paulo, SP 04023–062, Brazil.
E-mail: luis@reumato.epm.br

Summary

The aim of this study was to characterize a novel human autoantibody–autoantigen system represented as cytoplasmic discrete speckles (CDS) in indirect immunofluorescence (IIF). A distinct CDS IIF pattern represented by 3–20 discrete speckles dispersed throughout the cytoplasm was identified among other cytoplasmic speckled IIF patterns. The cytoplasmic domains labelled by human anti-CDS-1 antibodies did not co-localize with endosome/lysosome markers EEA1 and LAMP-2, but showed partial co-localization with glycine–tryptophan bodies (GWB). CDS-1 sera did not react with several cellular extracts in immunoblotting and did not immunoprecipitate recombinant GW182 or EEA1 proteins. The typical CDS-1 IIF labelling pattern was abolished after delipidation of HEp-2 cells. Moreover, CDS-1 sera reacted strongly with a lipid component co-migrating with phosphatidylethanolamine (PE) in high performance thin-layer chromatography (HPTLC)-immunostaining of HEp-2 cell total lipid extracts. The CDS-1 major molecular targets were established by electrospray ionization–mass spectrometry (ESI-MS), HPTLC-immunostaining and chemiluminescent enzyme-linked immunosorbent assay as diacyl-PE species, containing preferentially a cis-C18 : 1 fatty acid chain at C-2 of the glycerol moiety, namely 1,2-cis-C18 : 1-PE and 1-C16 : 0-2-cis-C18 : 1-PE. The clinical association of CDS-1 sera included a variety of systemic and organ-specific autoimmune diseases but they were also observed in patients with no evidence of autoimmune disease.

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