The Choice of Antibodies

The decision regarding whether to use a polyclonal antibody or monoclonal antibody depends on a number of factors, the most important of which are its intended use and whether the antibody is readily available from commercial suppliers or researchers. The concentration and purity levels of specific antibody are higher in monoclonal antibodies. However, polyclonal antibodies are known to have a higher affinity and a better specificity than monoclonal antibodies, because they are produced by a large number of B cell clones each generating antibodies to a specific epitope, and because polyclonal sera are a composite of antibodies with unique specificities (Lipman et al. 2005). 

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ELISAs can be used in two modes, qualitatively to determine the presence or absence, or quantitatively to determine the amount of antigen present. ELISA kits often depend on the adsorption of either the antibody or antigen to a solid phase, e.g., wells of a microtiter plate, surface of plastic beads, or plastic stick. The choice of antibody (or antibodies) used determines the specificity of the ELISA assay, which can range from genus-specific to strain-specific. The principle on which ELISA methods are based usually prevents them from being used for the determination of total microbial counts. However, they can be used to detect pathogens such as Salmonella spp.. Listeria spp. 

There are many commercial sources of monodonal antibodies recognizing the halogenated pyrimidines. The choice of antibody often depends on individual preference to one or other company. However, several points should be taken into account as the quality of the measurement will depend on the purity, affinity, and spedfidty of the antibody. For instance high affinity antibodies such as IU-4 (Caltag) will be required if low levels of BrdUrd are to be detected. 

The choice of fixation is a matter of experience, since the changes in the antigenicity of the component of interest resulting from the treatment with the fixative cannot be predicted. The epitope (amino acid sequence), against which the antibody was raised, may be hidden (masked), modified or completely lost as a result of an inadequate fixation (Shi et al. 2001). No ideal fixative has been found that can be used universally in immunohistochemistry. The choice of the adequate... 

While it is one of the most important and versatile transformations available to organic chemists, there is no unequivocal example of a biological counterpart. Hence, attempts to generate antibodies which could catalyse this reaction were seen as an important target. The major task in producing a Diels-Alderase antibody lies in the choice of a suitable haptenic structure, because the transition state for the reaction resembles product more closely than reactants (Fig. 12). The reaction product itself is an inappropriate hapten because it is likely to result in severe product inhibition of the catalyst, thereby preventing turnover. 

Antigens can be immobilized on a number of different membranes using one of several methods, and antigens bind differently to different types of membranes. The choice of a membrane is dependent on many factors including the particular antigen to be detected and the requirements of the experiment. To maximize detection sensitivity, it is advisable to use mock samples to test different types of membranes with the particular antigen-antibody combination to be used. 

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