The effects of affinity-purified anti-DNA antibodies from patients with systemic lupus erythematosus on the fluorescent antinuclear antibody assay using HEp-2 cells.

Abstract

The aim of this study was to clarify the effects of anti-dsDNA antibodies on the titer and the nuclear staining pattern(s) in a fluorescent antinuclear antibody (FANA) assay using HEp-2 cells. Anti-dsDNA derived from 14 patients with systemic lupus erythematosus (SLE) was individually affinity-purified. The anti-dsDNA titer of the purified anti-dsDNA solution was measured by radioimmunoassay (RIA) or by enzyme-linked immunosorbent assay (ELISA). In the FANA assay, the anti-dsDNA solution was diluted in a stepwise manner and its titer was expressed by the endpoint dilution. The nuclear staining pattern in the anti-dsDNA solution was examined at the 1:5 and 1:20 dilutions and at the endpoint dilution. The anti-dsDNA titers of the affinity-purified anti-dsDNA solution were high enough (13 to 126 IU/ml) to be measured by RIA. However, the antinuclear antibody (ANA) titers of this solution were relatively low: 1:20 to 1:320. In the study of nuclear staining the peripheral pattern was observed in nine of the 14 cases at a 1:5 dilution. However, at the endpoint dilution, all cases exhibited the homogeneous pattern. These findings indicate that in the FANA assay using HEp-2 cells, 1) although serum samples show high anti-dsDNA titers by RIA or by ELISA, the antibodies' direct contribution to ANA titers is limited, and 2) when samples reveal a homogeneous staining pattern at the endpoint dilution, this suggests the presence of anti-dsDNA.