Two key features that define the usefulness of polyclonal and mAb monoclonal antibodies are their specificity and sensitivity towards antigens. The specificity of an antibody depends on the relative affinity between its binding domains and the target antigen, while other molecules are also present.
Since many applications rely on the uses of mAb monoclonal antibodies or polyclonal antibodies to detect target molecules with specificity, this specificity is critical for immunologists and clinicians alike. Along with antigen specificity, the sensitivity of an antibody is an important parameter for determining its usefulness in the laboratory.
Highly sensitive antibodies are ideal for diagnostic applications such as immunoprecipitation, Western blotting, and enzyme-linked immunosorbent assays (ELISAs) because they can detect low levels of target antigens. Immunoprecipitation is an analytical technique that separates antigens from a mixture using antibodies that bind specifically to the antigen. The resulting antigen-antibody complex can then be further processed using immobilized antibodies or magnetic beads to isolate the complex before analysis.
Like immunoprecipitation, ELISA can use polyclonal antibody or monoclonal antibodies to detect target antigens in a solution. Indirect and sandwich ELISA are two forms of immunodetection that use two types of antibodies throughout the process: monoclonal antibodies are typically applied first (primary) because they have high specificity for the target antigen, and polyclonal antibodies are more useful as secondary reagents because they can amplify low signals with high sensitivity.
In addition to ELISA, antibodies can also be used in detection techniques such as immunohistochemistry and flow cytometry because they can detect antibody-antigen complexes in complex tissues or cells with high resolution.
Confirmation by manufacturers of antibody specificity and sensitivity allows immunodetection techniques such as ELISA to adopt various forms based on the antigen and antibody used, making these assays highly versatile. For example, highly sensitive tests to detect unknown pathogens in immunodetection will benefit from polyclonal antibody because they can recognize multiple epitopes on the antigen. If the pathogen or antigen has been characterized previously, monoclonal antibodies may be more appropriate for downstream applications to further characterize.
Outside of the laboratory, antibodies can be used to enhance, mimic or restore the immune system's ability to attack disease targets. Except for a few exceptions, monoclonal antibodies are better suited for therapeutic purposes than polyclonal antibodies because of their homogeneity, high specificity towards a single epitope, and low cross-reactivity. These features are particularly important for effective cancer therapy because tumor cells are able to evade or block the immune system. MAb monoclonal antibody therapy for cancer cells can work in several ways, including directly binding to induce cell death mechanisms and indirectly blocking tumor growth factors and blood supply.