Citazione:

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http://www.abcam.com/index.html?pageconfig=resource&rid=11269&pid=11287

SUMMARY

Polyclonal antibodies


Inexpensive to produce

Technology required is low

Skills required are low

Time scale is short

Produces large amounts of non specific antibodies

Recognizes multiple epitopes on any one antigen

Can be batch to batch variability


Monoclonal antibodyes


Expensive to produce

High technology required

Training is required for the technology use

Time scale is long for hybridomas

Recognizes only one epitope on an antigen

Can produce large amounts of specific antibodies but may be too specific

Once a hybridoma is made it is a constant and renewable source and all batches will be identical




Polyclonal antibodies

Facts:

Recognise multiple epitopes on any one antigen. Serum obtained will contain a heterogeneous complex mixture of antibodies of different affinity
Polyclonals are made up mainly of IgG subclass
Peptide immunogens are often used to generate polyclonal antibodies that target unique epitopes, especially for protein families of high homology

Antibody production:

Inexpensive to produce
Technology and skills required for production low
Production time scale is short
Polyclonal antibodies are not useful for probing specific domains of antigen because polyclonal antiserum will usually recognize many domains

General advantages:

Polyclonals will recognize multiple epitopes on any one antigen which has the following advantages:

Polyclonals can help amplify signal from target protein with low expression level, as the target protein will bind more than one antibody molecule on the multiple eptitopes. This would not be an advantage for quantification experiments e.g. in flow cytometry, as the results would become inaccurate.
Due to recognition of multiple epitopes, polyclonals can give better results in IP / ChIP
More tolerant of minor changes in the antigen, e.g., polymorphism, heterogeneity of glycosylation, or slight denaturation, than monoclonal (homogenous) antibodies.
They will identify proteins of high homology to the immunogen protein or to screen for the target protein in tissue samples from species other than that of the immunogen e.g. Polyclonal antibodies are sometimes used when the nature of the antigen in an untested species is not known. This also makes it important to check immunogen sequence for any cross-reactivity.
Polyclonal antibodies are often the preferred choice for detection of denatured proteins.
Multiple epitopes generally provide more robust detection.
Polyclonal antibodies not useful for probing specific domains of antigen, because antiserum will usually recognize many domains.

Disadvantages:

Prone to batch to batch variability.
They produce large amounts of non-specific antibodies which can sometimes give background signal in some applications.
Multiple epitopes make it important to check immunogen sequence for any cross-reactivity.

Monoclonal antibodies

Facts:

Detect only one epitope on the antigen.
They will consist of only one antibody subtype. Where a secondary antibody is required for detection, an antibody against the correct subclass should be chosen.

Antibody production

High technology required.
Training is required for the technology used.
Time scale is long for hybridomas.

Advantages:

Once hybridomas are made it is a constant and renewable source and all batches will be identical – useful for consistency and standardization of experimental procedures and results

Monoclonals detect one epitope only on any one antigen which has the following advantages:

Monoclonals usually have less background from staining of sections and cells. As they are more specifically detecting one target epitope, they are less likely to cross-react with other proteins.
Because of their specificity, monoclonal antibodies are excellent as the primary antibody in an assay, or for detecting antigens in tissue, and will often give significantly less background staining than polyclonal antibodies.
Compared to polyclonal antibodies, homogeneity of monoclonal antibodies is very high. If experimental conditions are kept constant, results from monoclonal antibodies will be highly reproducible, between experiments.
Specificity of monoclonal antibodies makes them extremely efficient for binding of antigen within a mixture of related molecules, such as in the case of affinity purification

Disadvantages:

They can produce large amounts of specific antibodies but may be too specific (e.g. less likely to detect in across a range of species)
More vulnerable to the loss of epitope through chemical treatment of the antigen than are polyclonal antibodies. This can be offset by pooling two or more monoclonal antibodies to the same antigen.

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Citazione:

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Tratto da: Monoclonal Versus Polyclonal Antibodies: Distinguishing Characteristics, Applications, and Information Resources

Polyclonal Versus Monoclonal Antibodies
The decision regarding whether to use a PAb or MAb de- pends 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. PAbs can be generated much more rapidly, at less expense, and with less technical skill than is required to produce MAbs. One can reasonably expect to obtain PAbs within several months of initiating immunizations, whereas the generation of hybridomas and subsequent production of MAbs can take up to a year or longer in some cases, therefore requiring considerably more expense and time. The availability of an “off the shelf” reagent eliminates the issues of time and, frequently, cost.
The principal advantages of MAbs are their homogene- ity and consistency. The monospecificity provided by MAbs is useful in evaluating changes in molecular confor- mation, protein-protein interactions, and phosphorylation states, and in identifying single members of protein fami- lies. It also allows for the potential of structural analysis (e.g., x-ray crystallography or gene sequencing) to be de- termined for the antibody on a molecular level. However, the monospecificity of MAbs may also limit their useful- ness. Small changes in the structure of an epitope (e.g., as a consequence of genetic polymorphism, glycosylation, and denaturation) can markedly affect the function of a MAb. For that reason, MAbs should be generated to the state of the antigen to which it will eventually need to bind. In contrast, because PAbs are heterogeneous and recognize a host of antigenic epitopes, the effect of change on a single or small number of epitopes is less likely to be significant. PAbs are also more stable over a broad pH and salt con- centration, whereas MAbs can be highly susceptible to small changes in both. Another key advantage of MAbs is that once the desired hybridoma has been generated, MAbs can be generated as a constant and renewable resource. In contrast, PAbs generated to the same antigen using multiple animals will differ among immunized animals, and their avidity may change as they are harvested over time. The quantity of PAbs obtained is limited by the size of the animal and its lifespan.
PAbs frequently have better specificity than MAbs be- cause they are produced by a large number of B cell clones each generating antibodies to a specific epitope, and poly- clonal sera are a composite of antibodies with unique speci- ficities. However, the concentration and purity levels of specific antibody are higher in MAbs. The concentration of specific antibody in polyclonal sera is typically 50 to 200 #1113103;g/mL, and the range of total Ig concentration in sera is between 5 and 20 mg/mL. In comparison, MAbs generated as ascites or in specialized cell culture vessels are frequently 10-fold higher in concentration and of much higher purity.
MAbs are not generally useful for assays that depend on antigen cross-linking (e.g., hemagglutination) unless di- meric or multimeric antigens or antigens bound to a solid phase are used. Additionally, they may not activate complement readily because activation requires the close proximity of Fc receptors. Modification of antibodies by covalently linking a fluorochrome or radionuclide may also alter anti- body binding. This potential is less of a concern when using PAbs, which recognize a host of epitopes, but it can be significant for MAbs if the change affects its monospecific binding site.
Many of the disadvantages of MAbs can be overcome by pooling and using multiple MAbs of desired specifici- ties. The pooled product is consistent over time and avail- able in limitless quantity. However, it is frequently difficult, too expensive, and too time consuming to identify multiple MAbs of desired specificity.

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