ImmunoassayImmunoassay is an assay that quantifies antigen (a stimulating molecule) or antibody (an immuno-response molecule) by immunochemical means. The antigen can be a relatively simple substance such as a drug, or a complex one such as a protein or a virus.
In an immunoassay, the reactants are first mixed so that a varying quantity of one (A) is added to a constant amount of the other (B). The formation of an immune (antigen-antibody) complex is measured as a function of the varied reactant (A). The result is represented by a ‘standard curve’ for reactant A. An unknown sample is tested by adding it to reactant B. The extent of the measured change is referred to as the standard curve, and thereby obtaining the amount of reactant A which produces a comparable change. That amount is represented as the content of reactant A in the unknown sample.
This type of immunoassay requires a direct detection of only the amount of immune complex or only the amount of residual free reactant. The immune complex can be measured by the formation of large aggregates, of small aggregates detected by light scattering, or by the evolution of heat in the reaction. If one of the reactants is initially fixed to a solid support such as the wall of a test tube or fragment of plastic, the support can be washed free of contaminants at the end of the reaction. The product of the reaction can then be assayed, for example, by immunofluorescence.
Web Resources On Immunoassay
U.S. EPA: Immunoassay
Wikipedia: Immunoassay
Book Resources On ImmunoassayImmunoassay by Eleftherios P. Diamandis
Analytical Chemistry by Robert Kellner, et al.
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