Human autoantibodies to diacyl-phosphatidylethanolamine recognize a specific set of discrete cytoplasmic domains.
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.
Rheumatology Division, Universidade Federal de São Paulo, Escola Paulista de Medicina (UNIFESP-EPM), Rua Botucatu 740, São Paulo, SP 04023-062, Brazil.
C C F C
CC
Laurino
M J
MJ
Fritzler
R A
RA
Mortara
N P
NP
Silva
I C
IC
Almeida
L E C
LE
Andrade
D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000032:analysis*; D001324:Autoantigens / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D022162:Cytoplasmic Vesicles / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal / Q000379:methods; D008875:Middle Aged; D010714:Phosphatidylethanolamines / Q000276:immunology*; D012189:Retrospective Studies
D001323:Autoantibodies; D001324:Autoantigens; D010714:Phosphatidylethanolamines