Fractionation of cortisol antisera by immunoadsorption chromatography: characterisation and use in an enzyme-linked immunosorbent assay (ELISA).

The use of affinity chromatography in the presence of 20% acetonitrile combined with a decreasing pH gradient has allowed the fractionation of two cortisol antisera into components of varying affinity. The high affinity fractions generate considerably improved ELISA standard curves compared to the intact sera but do not grossly alter the specificity of the antisera. Accordingly, the high affinity fraction of the least cross-reactive antiserum was used for a plasma cortisol ELISA. The cortisol ELISA, although returning slightly higher values than RIA, was comparable in the ability to distinguish dexamethasone suppression and cortisol response to synacthen and should thus prove of value in the assay of plasma cortisol.