Expression of IgM and IgG autoantibodies in pediatric and adult systemic lupus erythematosus

Abstract

To compare patterns of autoantibody responses in pediatric and adult patients with systemic lupus erythematosus (SLE). IgG and IgM antibodies to single-stranded DNA (ssDNA), Sm, and the 70-kDa protein component of the RNP antigen (70-kDa RNP) were measured in 29 pediatric and 36 adult patients by enzyme-linked immunosorbent assays. Antibodies of either isotype to ssDNA, Sm, and 70-kDa RNP were present in 64, 58, and 79% of pediatric patients, respectively, comparable to prevalences of these autoantibodies in the adult SLE patients. Pediatric SLE patients were more likely than adult patients to have IgM anti-Sm antibodies (41.4% vs 13.9%, P = 0.02) and tended to more commonly express IgM anti-70-kDa RNP and IgM anti-ssDNA antibodies. The prominence of IgM autoantibody responses among pediatric SLE patients was shown by multiple logistic regression analysis to be related to total IgM concentrations and not related to age or duration of disease. Sequential serum samples available from several pediatric patients revealed the maintenance of similar patterns of isotype responses over time in approximately one-half of patients. In those patients whose responses changed over time, the variations in isotype expression were consistent with maturation of antibody responses of each specificity. While these results demonstrate similarities in autoimmune reactivities between pediatric and adult SLE patients, the serologic study of pediatric patients may provide an opportunity to more readily investigate the evolution of autoantibody responses.