FACTOID #53: If you thought Antarctica was inhospitable, think again - its land area is only ninety-eight percent ice. Reassuringly, the other 2% is categorised as "barren rock".
Antinuclear antibodies (ANAs, also known as antinuclear factor or ANF) are detected in a large group of autoimmune disorders. The presence of ANA is indicative of lupus erythematosus, though they also appear in some other auto-immune diseases such as Sjögren's syndrome, rheumatoid arthritis, autoimmune hepatitis, scleroderma and dermatomyositis, and various non-rheumatological conditions associated with tissue damage.
Following detection of a high titer of ANAs (e.g. 1:160), various subtypes are determined (Kavanaugh et al 2000). This is nowadays ususally done on cells of the HEp-2 cell line. Examples include:
Anti-ENA (extractable nuclear antigen)
Anti-dsDNA (double-stranded DNA)
Anti-Jo (SS-A)
Anti-Ro (SS-B)
Anti-Sm (Smith antigen)
Anti-nRNP (nuclear ribonucleoproteins)
Anti-Scl-70
Anti-topoisomerase I
Anti-centromere
History
The LE cell was discovered in bone marrow in 1948 by Hargraves et al. This was the first indication that processes affecting the cell nucleus were responsible for lupus erythematosus (LE). In the 1950s, progressively more sensitive and specific ANA serology tests became available.
Hargraves M, Richmond H, Morton R. Presentation of two bone marrow components, the tart cell and the LE cell. Mayo Clin Proc 1948;27:25–28.
Kavanaugh A, Tomar R, Reveille J, Solomon DH, Homburger HA. Guidelines for clinical use of the antinuclear antibody test and tests for specific autoantibodies to nuclear antigens. American College of Pathologists. Arch Pathol Lab Med 2000;124:71-81. Medline abstract (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10629135) (PMID 10629135).
Antinuclear antibodies are produced in some diseases and may be used to assist in diagnosis by sub-typing such antibodies and detecting their presence in an individual.
Antinuclearfactor - antinuclear antibody ANF / ANA are raised most typically in autoimmune disease They are not diagnostic, and frequently occur in low titer in normal.
Rheumatoid factor is positive in only 85% of clinical rheumatoid arthritis patients, and diagnosis may be made in absence of the rheumatoid factor.
Often, use of the term “factor” indicates that the chemical nature of the substance or its mechanism of action is unknown, as in endocrinology, where “factors” are renamed as “hormones” when their chemical nature is determined.
VI a factor (accelerin) previously thought to be an activated form of factor V. It no longer is considered in the scheme of hemostasis, and hence it is currently assigned neither a name nor a function.
VIII antihemophilic factor (AHF): a relatively storage-labile factor participating in the intrinsic pathway of blood coagulation, acting (in concert with von Willebrand factor) as a cofactor in the activation of factor X. Deficiency, an X-linked recessive trait, causes hemophilia A (classical hemophilia).
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