Objectives: To determine the frequency of antibodies to chromatin components in juvenile systemic lupus erythematosus (JSLE), and to correlate the presence of these autoantibodies with clinical manifestations and disease activity.
Methods: Anti-chromatin (anti-CHR), anti-nucleosome core particle (anti-NCS) and anti-dsDNA antibodies were measured in 175 individuals, including 37 patients with active JSLE and 41 with inactive disease, 47 non-lupus autoimmune disease patients (non-lupus AD), and 50 healthy children. An in-house ELISA was developed with purified nucleosome core particles from calf thymus to determine IgG and IgG3 anti-NCS antibodies. Anti-CHR and anti-dsDNA antibodies were detected by commercial ELISA kits (INOVA).
Results: Anti-NCS and anti-CHR antibodies exhibited high specificity for JSLE and similar frequency in active and inactive JSLE. Anti-CHR and IgG/IgG3 anti-NCS serum levels did not differ between active and inactive JSLE. SLEDAI correlated with anti-dsDNA antibodies but not with antibodies to other chromatin components. There was association of anti-dsDNA, anti-CHR and IgG/IgG3 anti-NCS antibodies with proteinuria and low C4 serum levels. Anti-NCS antibodies in the absence of anti-dsDNA were observed in 14% of the JSLE patients.
Conclusions: Our data indicate that anti-NCS and anti-CHR antibodies are relevant diagnostic markers for JSLE and appear to be correlated with JSLE lupus nephritis activity. IgG3 isotype anti-NCS antibodies do not seem to be more relevant than IgG anti-NCS antibodies as markers of disease activity or active nephritis in JSLE.