title: Family distribution of anti-F(ab')2 antibodies in relatives of patients with systemic lupus erythematosus.
abstract: Recently we reported an inverse relationship between the levels of anti-F(ab')2 antibodies and disease activity in systemic lupus erythematosus (SLE). The present study focused on anti-F(ab')2 antibodies in unaffected relatives of SLE patients. Sixty sera from first degree family members from 11 SLE families and 49 sera from 8 control families were studied. Percentage of SLE family members with anti-DNA antibodies (15%) was higher than than control family sera (8%, P less than 0.05). Anti-F(ab')2 antibodies were measured using ELISA assays. The SLE family sera had higher amounts of anti-F(ab')2 antibodies than the normal control family group (P = 0.0051). In an effort to determine if anti-F(ab')2 antibodies found in high titres in the sera of some SLE family members had specificity for the F(ab')2 fragment of anti-DNA antibodies of the SLE relative patients, DNA-anti-DNA inhibition experiments were performed using anti-F(ab')2 prepared from the relative in parallel with anti-F(ab')2 prepared from normal controls with equivalent high titres of serum anti-F(ab')2. Inhibition exhibited by anti-F(ab')2 of first degree relatives was higher than that obtained from control normal donors (P less than 0.02). Such differences in inhibition were not recorded using a control tetanus toxoid-anti-tetanus toxoid assay. In direct binding ELISA experiments, peroxidase-conjugated anti-F(ab')2 antibodies from the same first degree relative showed high relative specificity against purified anti-DNA antibodies of his SLE proband when compared to those obtained against different anti-DNA antibodies isolated from unrelated SLE patients (P less than 0.001). Such a substantial difference was not observed in parallel experiments using peroxidase conjugated anti-F(ab')2 antibodies from normal controls unrelated to SLE subjects.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000888:Antibodies, Anti-Idiotypic / Q000032:analysis*; D000974:Antibodies, Antinuclear / Q000032:analysis; D000918:Antibody Specificity; D002648:Child; D004277:DNA, Single-Stranded / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology*; D008180:Lupus Erythematosus, Systemic / Q000235:genetics* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D013745:Tetanus Toxoid / Q000276:immunology
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000974:Antibodies, Antinuclear; D004277:DNA, Single-Stranded; D007140:Immunoglobulin Fab Fragments; D013745:Tetanus Toxoid