Induction of in vitro heart block is not restricted to affinity purified anti-52 kDa Ro/SSA antibody from mothers of children with neonatal lupus.
The ability of affinity purified anti-52 kDa Ro/SSA antibody from patients without obstetric history of neonatal lupus to cause heart block using an experimental model was investigated. IgG-enriched fractions from sera of 20 systemic lupus erythematosus (SLE) and one Sjögren's syndrome (SS) all positives for anti-Ro/SSA antibodies as detected by CIE, were perfused on isolated whole rabbit hearts. Only six (29%) samples induced A-V block, five of them presenting low anti-Ro/SSA titre. All of them recognized the 52 kDa isoform on ELISA whereas only one had a concomitant binding to the 60 kDa protein. Moreover, affinity purified antibodies from two sera previously known to induce A-V block were obtained by affinity chromatography using a column containing the full-length 52 kDa Ro/SSA fusion protein. Paired eluate and effluent devoid of anti-52 kDa activity from the same patient were individually perfused in whole hearts. The ability to cause cardiac blockade was restricted to the affinity anti-52 kDa eluates. In addition, anti-52 kDa eluates from three IgG fractions that primarily failed to induce blockade remained ineffective. The present study has added to our knowledge that affinity anti-52 kDa Ro/SSA antibodies from mothers with healthy infants are capable of causing in vitro cardiac conduction disturbances. A prospective follow up of these patients will better delineate the clinical usefulness of this experimental model.
Viana
V S
VS
Division of Rheumatic Diseases, University of São Paulo, SP, Brazil.
Garcia
S
S
Nascimento
J H
JH
Elkon
K B
KB
Brot
N
N
Campos de Carvalho
A C
AC
Bonfá
E
E
D000974:Antibodies, Antinuclear / Q000009:adverse effects* / Q000737:chemistry / Q000302:isolation & purification; D018501:Antirheumatic Agents / Q000009:adverse effects; D001324:Autoantigens / Q000276:immunology; D003378:Counterimmunoelectrophoresis; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006327:Heart Block / Q000139:chemically induced*; D006329:Heart Conduction System / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D007231:Infant, Newborn; D008180:Lupus Erythematosus, Systemic / Q000151:congenital* / Q000276:immunology; D009035:Mothers; D011233:Precipitin Tests; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins / Q000276:immunology; D000097585:SS-B Antigen; D000099207:SS-A Antigen
D000974:Antibodies, Antinuclear; D018501:Antirheumatic Agents; D001324:Autoantigens; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D000097585:SS-B Antigen; D000099207:SS-A Antigen; C116006:RO60 protein, human