INDUCTION OF IN-VITRO HEART-BLOCK IS NOT RESTRICTED TO AFFINITY-PURIFIED ANTI-52 KDA RO SSA ANTIBODY FROM MOTHERS OF CHILDREN WITH NEONATALLUPUS/

The ability of affinity purified anti-52 kDa Ro/SSA antibody from pati ents without obstetric history of neonatal lupus to cause heart block using an experimental model was investigated. IgG-enriched fractions f rom sera of 20 systemic lupus erythematosus (SLE) and one Sjogren's sy ndrome (SS) all positives for anti-Ro/SSA antibodies as detected by CI E, were perfused on isolated whole rabbit hearts. Only six (29%) sampl es induced A-V block, five of them presenting low anti-Ro/SSA titre. A ll of them recognized the 52 kDa isoform on ELISA whereas only one had a concomitant binding to the 60 kDa protein. Moreover, affinity purif ied antibodies from two sera previously known to induce A-V block were obtained by affinity chromatography using a column containing the ful l-length 52 kDa Ro/SSA fusion protein. Paired eluate and effluent devo id of anti-52 kDa activity from the same patient were individually per fused in whole hearts. The ability to cause cardiac blockade was restr icted to the affinity anti-52 kDa eluates. In addition, anti-52 kDa el uates from three IgG fractions that primarily failed to induce blockad e remained ineffective. The present study has added to our knowledge t hat affinity anti-52 kDa Ro/SSA antibodies from mothers with healthy i nfants 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.