Immunochemical methods using specific antibodies, applications

Fluorescent Staining. Certain methods of tissue staining differentially detect the presence of particular chemical components in cells. One approach is to use a fluorescent label to trace components inside the cell. Fluorescent staining not only attests to the presence or absence of certain components in cells but also provides their precise localization in a particular cell or tissue type. For example, immunochem-istry uses fluorescent antibodies that specifically bind with the target structures in the tissue so that the labeled antibodies will highlight the presence of the structures of interest in the analyzed specimen. Some applications of these techniques are staining of virus-infected cells in tissues and detection of immune-complex deposition in the kidneys and skin of patients with lupus. 

Although both polyclonal and monoclonal antibodies have been effectively used in immunochemical assays, only the latter can provide the high specificity required in some applications. Antibody specificity, on the other hand, is both a major advantage and disadvantage for immunochemical methods. It allows for highly selective detection of analytes but at the same time may complicate the development of multiresidue methods. Moreover, production of monoclonal antibodies requires special expertise and it is much more expensive than polyclonal antibodies. Thus, in cases where a range of analytes similar in molecular structure are required to be determined, a polyclonal may be more suitable than a monoclonal antibody. 

The immunochemical interaction between the antigen and antibody is very specific. By labeling either the antigen or antibody, the method s sensitivity is increased. The most frequently used labels to increase sensitivity are radionucHdes (see Radioisotopes) where the assay process is called radioimmunoassay (RIA), or en2ymes where the assay is named en2yme immunoassay (ElA) (see Enzyme applications). 

Immunochemical and molecular methods are useful for detecting specific fungi from air samples. These techniques are finding greater applications as monoclonal antibodies and DNA probes become available for fungi with known health effects. 

Using the characteristic of a high-affinity complex between avidin and biotin, biotinylated antibodies have wide applications in various immunochemical assays, especially where signal amplification is required. A method is described here for the biotinylation of immunoglobulins. The procedure utilizes water-soluble succinimidyl ester of biotin that reacts with primary amines of the lysine residues or the amino terminus on the antibody to form amide bonds. The method is simple and specific and results in stable conjugates retaining full immunologic activity. 

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