Assay for adrenal autoantigen

A method for diagnosing Addison's disease in a patient, comprising:

• obtaining a sample containing antibodies from the patient;
• and
• detecting, in the sample, the presence or absence of antibodies which specifically bind a substantially pure microsomal protein comprising an epitope for adrenal autoantibody, having an observed molecular weight of approximately 55,000 as measured by gel electrophoresis and obtained by:
• homogenizing mammalian adrenal glands,
• subjecting the homogenate to differential centrifugation to obtain a microsome fraction,
• suspending the microsome fraction in a phosphate buffer,
• centrifuging the suspension in the presence of sodium cholate to form a supernatant,
• adding polyethylene glycol and further sodium cholate to the supernatant and mixing the supematant,
• centrifuging the thus mixed supernatant to form a pellet,
• resuspending the pellet in aqueous sodium cholate to form a suspension,
• dialyzing the suspension obtained by resuspending the pellet against aqueous sodium cholate to form a solubilized microsome preparation, and
• purifying the solubilized microsome preparation by column chromatography on a C.sub.8 reversed phase column equilibrated with 50 mM phosphate buffer, pH 7.0, 20% glycerol, 0.1 mM EDTA, 0.1 mM DTT, and eluted with increasing concentration of detergent to obtain a column fraction corresponding to peak VI of FIG. 1 containing the microsomal protein;
• wherein presence of said antibodies in said sample is indicative of Addison's disease in the patient.