21-Hydroxylase Antibody

The 21-hydroxylase autoantibody (21-OH Ab) ELISA kit is intended for use by professional persons only, for the quantitative determination of 21-OH Ab in human serum. Autoimmune destruction of the adrenal cortex is the most common cause of Addison’s disease and autoantibodies to the adrenal specific enzyme steroid 21-hydroxylase are important markers of adrenal autoimmunity. This can be the case if the disease presents as Addison’s disease or as part of the autoimmune polyglandular syndromes (APS) type I or type II.

In the 21-OH Ab ELISA kit, 21-OH Ab in patients’ sera, calibrators and controls are allowed to interact with 21-OH coated onto ELISA plate wells. After a 16 – 20 hour incubation, the samples are discarded leaving 21-OH Ab bound to the 21-OH coated on the wells. 21-OH-Biotin is added in a 2nd incubation step where, through the ability of 21-OH Ab to act divalently, a bridge is formed between the 21-OH immobilised on the plate and 21-OHBiotin. The amount of 21-OH-Biotin bound is then determined in a 3rd incubation step involving addition of streptavidin peroxidase (SA-POD), which binds specifically to Biotin. Excess, unbound SA-POD is then washed away and addition of the peroxidase substrate 3,3’,5,5’-tetramethlybenzidine (TMB) results in formation of a blue colour. This reaction is stopped by the addition of a stop solution, causing the well contents to turn yellow. The absorbance of the yellow reaction mixture at 450nm and 405nm is then read using an ELISA plate reader. A higher absorbance indicates the presence of 21-OH Ab in the test sample. Reading at 405nm allows quantitation of high absorbances. It is recommended that values below 1 U/ml should be measured at 450nm. If it is possible to read at only one wavelength 405nm may be used. The measuring interval is 0.3 – 100 U/ml (arbitrary units).

• E Lübke, A Freiburg, GO Skeie, B Kolmerer, S Labeit, JA Aarli, NE Gilhus, R Wollmann, M Wussling, JC Ruegg, WA Linke Striational autoantibodies in myasthenia gravis patients recognize I-band titin epitopes
  J Neuroimmunol 1998;81:98-108
• RD Voltz, WC Albrich, A Nägele, F Schumm, M Wick, A Freiburg, M Gautel, HT Thaler, J Aarli, Th Kirchner, R Hohlfeld Paraneoplastic myasthenia gravis: Detection of anti-MGT30 (titin) antibodies predicts thymic epithelial tumor
  Neurology 1997;49:1454-1457
• M Gautel, A Lakey, DP Barlow, Z Holmes, S Scales, K Leonard, S Labeit, A Mygland, NE Gilhus, JA Aarli Titin antibodies in myasthenia gravis: Identification of a major immunogenic region of titin
  Neurology 1993;43:1581-1585