ANTIHISTONE ANTIBODIES IN SYSTEMIC LUPUS-ERYTHEMATOSUS - ASSAY DEPENDENCY AND EFFECTS OF UBIQUITINATION AND SERUM DNA

Objective. Antihistone antibodies occur in systemic lupus erythematosu s (SLE), but there are many discrepancies in their reported prevalence , isotype, specificity and correlation with disease symptoms. We exami ned the role of the assay and the influence of serum DNA as possible c auses of these discrepancies. In addition, we sought to confirm the pr esence of antibodies to ubiquitin and ubiquitinated H2A (uH2A). Method s. Western blot and enzyme linked immunosorbent assay (ELISA). Results . Sera displayed substantial differences between ELISA and Western blo t in reactivity to individual histones when all reagents were nearly i dentical, indicating that subtle differences in the solid phase adsorb ents have pronounced effect on histone antigenicity. No uniform patter n of antibody reactivity with the 5 histones was apparent with either assay. For most sera, digestion with DNase caused only minor decrease in binding to histones and no histone class showed particular sensitiv ity to this treatment. In agreement with most other studies, no signif icant correlation between histone binding and symptoms was found. Just 2 of 40 sera showed detectable binding to ubiquitin or uH2A. Conclusi on. Although IgG antihistone antibodies were detected in 53-55% of pat ients with SLE with active disease, the sensitivity of antibody activi ty to assay conditions, patient variability, and lack of correlation w ith symptoms compromise the clinical utility of measuring antihistone antibodies by Western blot or ELISA. We were also unable to confirm th at ubiquitin and uH2A are major antigens recognized by antibodies in S LE.