A COMPETITIVE ENZYME-LINKED IMMUNOASSAY FOR THE QUANTITATION OF SOLUBLE HUMAN-IMMUNOGLOBULIN-G AND ALBUMIN IN NANOGRAM AMOUNTS

Background: Some clinical and experimental questions require quantitat ion of soluble serum proteins in amounts lower than those which are de tectable by radial immunodiffusion (RID) or nephelometry. Materials an d Methods: We describe a competitive enzyme-linked immunoassay (CELIA) for the quantitation of minor amounts of soluble human IgG and albumi n. Results: The assay enables the detection of IgG and albumin in the range of 5 to 125 ng/ml. Conclusions: Besides its high sensitivity, th e main advantage of this double-step technique is that the sample-spec ific primary antibody is not needed in an enzyme-conjugated form becau se of the use of a labelled secondary antibody.