Monoclonal vs Polyclonal Antibodies
In this article, we describe polyclonal and monoclonal antibodies in more detail and consider how each type may be used for various applications.
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Contents
What are polyclonal antibodies?
How do you generate polyclonal antibodies for research?
Differences between monoclonal and polyclonal antibodies
What are monoclonal antibodies?
How do you generate monoclonal antibodies for research?
Antibodies are immunological proteins that play fundamental roles in host defense against infectious agents such as viruses, bacteria and fungi. The immunological functions of these Y-shaped proteins are determined by their ability to bind antigens, the molecules released by or found upon cells that stimulate an immune response.
Beyond their roles in host immunity, antibodies prove to be valuable for research and therapeutic purposes too. Two types of antibodies – polyclonal and monoclonal – provide research scientists with distinct ways to detect or quantify target antigens largely due to differences in specificity and affinity. In this article, we describe polyclonal and monoclonal antibodies in more detail and consider how each type may be used for various applications.
What are polyclonal antibodies?
Once surveilling immune cells detect antigens in a host, the immune system undergoes a cascade of molecular events that induce the production of polyclonal antibodies by stimulated B cells. Polyclonal antibodies1 consist of biochemically dissimilar paratopes, the antigen-binding sites on the extended “arms” of an antibody, that enable specific binding to different binding sites on the same target antigen.
Polyclonal antibodies are attractive for research applications due to a combination of their high affinity towards the antigen of interest and their relative tolerance to minor changes exhibited by the target antigen in solution. For example, polyclonal antibodies generally display higher sensitivity than their monoclonal counterparts in diagnostic assays due to their biophysical diversity towards a target antigen. These features can also contribute to the clearance of pathogens more effectively2 than monoclonal antibodies. However, the feasibility of using polyclonal antibodies at scale is limited by factors such as our inability to industrially reproduce these proteins with consistency.
How do you generate polyclonal antibodies for research?
Differences between monoclonal and polyclonal antibodies
The differences between monoclonal and polyclonal antibodies. Credit: Technology Networks
What are monoclonal antibodies?
How do you generate monoclonal antibodies for research?
Monoclonal vs polyclonal antibodies - key differences
| Properties | Monoclonal Antibodies | Polyclonal Antibodies |
| Population of antibodies | Homogeneous | Heterogeneous |
| Binding specificity | Recognize a single epitope on a target antigen | Recognize multiple epitopes on a target antigen |
| Sensitivity | Better for protein quantitation | High for low-quantity proteins |
| Cross-reactivity | Lower due to high specificity | Higher due to biophysical diversity |
| Cost to produce | More expensive | Inexpensive |
| Origin | Single lineage of stimulated B cells; hybridomas | Multiple lineages of stimulated B cells |
Uses of polyclonal and monoclonal antibodies
Two of the key features that define the usefulness of polyclonal and monoclonal antibodies involves their respective specificity and sensitivity to an antigen. The specificity of an antibody is determined by the relative affinity between its binding domain and the target antigen while other molecules are present. The exploitation of this specificity is essential for immunological researchers and clinicians since many applications utilize polyclonal and/or monoclonal antibodies to specifically detect target molecules. In conjunction with antigen specificity, the sensitivity of an antibody is an important parameter that determines its usefulness in the lab.
High sensitivity antibodies are well suited for diagnostic applications5 like immunoprecipitation, lateral flow assay, immunohistochemistry, western blot and enzyme-linked immunosorbent assay (ELISA) due to their ability to recognize low levels of target antigen. Immunoprecipitation is an analytical technique that isolates an antigen from a mixture by using an antibody that specifically binds the antigen. The resulting antigen-antibody complexes can then be further processed by an immobilized antibody or magnetic beads, which allows the antigen-antibody complexes to be separated from the mixture prior to analysis.
Like immunoprecipitation, ELISAs6 can use polyclonal or monoclonal antibodies to detect a target antigen in solution. Indirect and sandwich ELISAs are two immunoassay forms that use both types of antibodies throughout their procedures: monoclonal antibodies are typically applied first (primary) due to their high specificity to the target antigen; polyclonal antibodies are more useful as the secondary reagent due to their ability to amplify a low signal with high sensitivity.7 Beyond ELISAs, antibodies are useful for detection techniques like immunohistochemistry and flow cytometry since they can detect antibody-antigen constructs within a complex tissue or cell with high resolution.
Confirmation of antibody specificity and sensitivity by manufacturers allow immunoassays like ELISAs to take on different forms depending on how the antigens and antibodies are used, which make these tests highly versatile. For example, an immunoassay that requires a highly sensitive test to detect an unknown pathogen would benefit from polyclonal antibodies due to their ability to recognize multiple epitopes on an antigen. If a pathogen or antigen has previously been characterized, then it may be more appropriate to use monoclonal antibodies in downstream applications for further characterization.
Outside of the laboratory, antibodies can be used to enhance, mimic or restore the immune system’s ability to attack disease targets. With some exceptions, monoclonal antibodies are better suited for therapeutic purposes than polyclonal antibodies due to their homogeneity, high specificity to a single epitope and their low degree of cross-reactivity.8 These properties are especially important for effective cancer therapies since tumor cells are capable of evading or blocking the immune system. Some of the ways monoclonal antibody therapies function against cancer cells include mechanisms that involve direct binding to induce cell death and indirect mechanisms that block tumors from growth factors and blood supply.9
