DNA Double-Stranded IgG Antibody Titer, IFA

Code
900.0470
Name
DNA Double-Stranded IgG Antibody Titer, IFA
Category
None
Department
None
Start Date
05/16/2012
Expiration Date
Synonyms
Anti-nDNA, Anti-dsDNA, DNA Autoantibodies, Double-Stranded (Crithidia), Double-Stranded DNA Antibody, Native DNA Antibody
CPT Codes
86256
Site
SBMF
Reference Test
28157
ATLAS Test Code

Specimen Information

Type

Gold, SST

Volume

1.0 mL

Transport Info

Refrigerated

Fasting Required?
False
Patient Instructions

Reference Range

No antibody detected

Methodology

Indirect Fluorescent Antibody (IFA)

Clinical Significance

Patients with systemic lupus erythematosus (SLE) may produce antibodies to a variety of nuclear antigens, but antibodies directed against Sm (Smith antigen) and nDNA show the highest correlation with disease. Antibodies directed against Sm demonstrate a speckled ANA staining pattern while antibodies directed against nDNA generally demonstrate a homogeneous ANA staining pattern. Although low levels of anti-nDNA antibodies may be present in the serum of patients with rheumatoid arthritis, Sjögren's syndrome, progressive systemic sclerosis, dermatomyositis, discoid lupus erythematosus, and mixed connective tissue disease, high levels of nRNA antibodies are seen almost exclusively in SLE. Antibodies against nDNA are thought to be involved in the pathogenesis of the most severe variants of SLE when deposited as immune complexes. Antibodies to nDNA occur in high titer, and, because they correlate with disease activity, their detection is important in the management of SLE patients.

Several assays are available for the detection of anti-nDNA antibodies. The most commonly used methods include indirect immunofluorescence, radioimmunoassay, counterimmunoelectrophoresis, and immunodiffusion. The Immuno Concepts IgG anti-nDNA test system is an indirect fluorescent antibody (IFA) method. Serum antibody, reactive to nDNA, is detected by staining of the kinetoplast within the organism Crithidia luciliae. C. luciliae is a parasite of the blowfly and is non-pathogenic to humans. The kinetoplast of these hemoflagellates is part of the large mitochondrion in which the helical nDNA is concentrated. In electron micrographs, the kinetoplast appears as a slightly concave, disc-shaped structure contining mitochondrial cristae and a fibrous DNA mass. The kinetoplast is found between the centrally located nucleus and the basal body of the flagellum. Because the kinetoplast nDNA contains no single-stranded DNA (ssDNA) contaminants, potential problems of ssDNA false-positive reactions, which may occur with calf thymus DNA radioimmunoassay, are virtually eliminated.

The Immuno Concepts IgG anti-nDNA test uses the indirect fluorescent antibody technique first described by Weller and Coons. Patient samples are incubated with antigen substrate to allow specific binding of auto-antibodies to kinetoplast nDNA. If anti-nDNA antibodies are present, a stable antigen-antibody complex is formed. After washing to remove non-specific antibodies, the substrate is incubated with an anti-human antibody reagent conjugated to fluorescein. When results are positive, there is the formation of a stable three-part complex consisting of fluorescent antibody bound to human anti-nDNA antibody which is bound to nDNA antigen. This complex can be visualized with the aid of a fluorescent microscope. In positive samples, the kinetoplast or the kinetoplast and nucleus will show a bright apple green fluorescence within the Crithidia luciliae organisms. If the sample is negative for IgG anti-nDNA antibodies, the kinetoplast will show no fluorescence.

Reference: IgG Anti-nDNA Fluorescent Test System, Immuno Concepts, 2003

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