Difference Between Monoclonal and Polyclonal Antibodies

 Main Difference – Monoclonal vs Polyclonal Antibodies

Antibodies are a type of globular proteins produced by the plasma B cells in response to a specific antigen. An antigen can be a foreign molecule that interacts with the cells of the immune system, triggering an immune response. The molecules on the antigens to which the antibodies attach themselves are called epitopes. The region of the antibody which binds to the epitope is called a paratope. Monoclonal antibodies and polyclonal antibodies are the two varieties of antibodies, which are used in therapeutics as well as in research applications. Both monoclonal and polyclonal antibodies interact with the same antigen. The main difference between monoclonal and polyclonal antibodies is that monoclonal antibodies are produced by the same clone of plasma B cells, and they bind to a unique epitope whereas polyclonal antibodies are produced by different clones of plasma B cells, and they bind to the different epitopes in the same antigen.  

Key Areas Covered

1. What are Monoclonal Antibodies
      – Definition, Production, Usage
2. What are Polyclonal Antibodies
      – Definition, Production, Usage
3. What are the Similarities Between Monoclonal and Polyclonal Antibodies
      – Outline of Common Features
4. What is the Difference Between Monoclonal and Polyclonal Antibodies
      – Comparison of Key Differences

Key Terms: Antigen, Epitope, Immunization, Monoclonal Antibodies, Paratopes, Plasma B Cells, Polyclonal Antibodies

What are Monoclonal Antibodies

Monoclonal antibodies refer to a homogeneous population of antibodies which are produced by a single clone of plasma B cells. This means the plasma B cell clone that produces a particular monoclonal antibody type is originated from a common ancestral plasma B cell. The plasma B cells used for this purpose should only be harvested from a specific location. First of all, the epitope, which is subjected for the production of monoclonal antibodies, should be injected to a particular animal. This process is called immunization. Then, the animal may produce antibodies against that epitope inside the body. Next, the immune cells should be harvested from a particular location. These plasma B cells are fused with the myeloma cell to obtain an immortal population of hybridoma cells. The hybridoma cells are cultured in HAT medium in order to obtain large populations of monoclonal plasma B hybridoma cells. Monoclonal antibodies can be harvested from culture vessels, The process of the production of the monoclonal antibodies is shown in figure 1.

Figure 1: Production of the Monoclonal Antibodies

Monoclonal antibodies can only recognize and bind to a specific epitope on the antigen. Therefore, these antibodies can be used to identify the presence of a particular organism which causes disease to the host. Therefore, monoclonal antibodies are mostly used as therapeutic agents.

What are Polyclonal Antibodies

Polyclonal antibodies refer to a mixture of immunoglobulin molecules which are secreted against a particular antigen; each antibody recognizes different epitopes. This means polyclonal antibodies are a heterogeneous mixture of antibodies. Each type of antibodies in the mixture are originated from a specific clone of plasma B cells. Thereby, the production of polyclonal antibodies employs multiple clones of plasma B cells. Immunization is the first step of the production of polyclonal antibodies as well. An animal can be immunized by a particular antigen. This antigen may contain several epitopes. The immune system produces different antibodies against each of the epitopes on the injected antigen. Polyclonal antibodies can be harvested from the serum of the animal directly. The process of the production of polyclonal antibodies is shown in figure 2.

Figure 2: Production of Polyclonal Antibodies

Polyclonal antibodies bind to multiple epitopes of the same antigen. This increases the capacity of detection of a particular antigen.

Similarities Between Monoclonal and Polyclonal Antibodies

• Both monoclonal and polyclonal antibodies are two varieties of antibodies.
• Both monoclonal and polyclonal antibodies are produced by plasma B cells.
• Both monoclonal and polyclonal antibodies interact with the same antigen.

Difference Between Monoclonal and Polyclonal Antibodies

Definition

Monoclonal Antibodies: Monoclonal antibodies refer to a homogeneous population of antibodies that are produced by a single clone of plasma B cells.

Polyclonal Antibodies: Polyclonal antibodies refer to a mixture of immunoglobulin molecules that are secreted against a particular antigen.

Produced by

Monoclonal Antibodies: Monoclonal antibodies are produced by the same clone of plasma B cells.

Polyclonal Antibodies: Polyclonal antibodies are produced by different clones of plasma B cells.

Hybridoma Cell Lines

Monoclonal Antibodies: The production of monoclonal antibodies requires the production of hybridoma cell lines.

Polyclonal Antibodies: Polyclonal antibody production does not require hybridoma cells lines since the antibodies can be harvested directly from the serum.

Antibody Population

Monoclonal Antibodies: Monoclonal antibodies are a homogeneous antibody population.

Polyclonal Antibodies: Polyclonal antibodies are a heterogeneous antibody population.

Interaction

Monoclonal Antibodies: Monoclonal antibodies interact with a particular epitope on the antigen.

Polyclonal Antibodies: Polyclonal antibodies interact with different epitopes on the same antigen.

Cost

Monoclonal Antibodies: Monoclonal antibodies are expensive to produce.

Polyclonal Antibodies: Polyclonal antibodies are inexpensive to produce.

Training

Monoclonal Antibodies: Skills are required to handle the technology for the production of monoclonal antibodies.

Polyclonal Antibodies: Fewer skills are required for the production of polyclonal antibodies.

Time taken for Production

Monoclonal Antibodies: The production of monoclonal antibodies require time.

Polyclonal Antibodies: Less time is taken for the production of polyclonal antibodies.

Cross Reactivity

Monoclonal Antibodies: Monoclonal antibodies possess less cross reactivity.

Polyclonal Antibodies: Polyclonal antibodies possess comparatively high cross reactivity.

Uses

Monoclonal Antibodies: Monoclonal antibodies are used as therapeutic drugs.

Polyclonal Antibodies: Polyclonal antibodies are used in general research applications.

Advantages

Monoclonal Antibodies: Immortal supply, high specificity, and high reproducibility are the advantages of the monoclonal antibodies.

Polyclonal Antibodies: High affinity, tolerant of minor changes, and more robust detection are advantages of the polyclonal antibodies.

Conclusion

Monoclonal and polyclonal antibodies are two types of antibodies that are used for different purposes. Monoclonal antibodies are produced by the same clone of plasma B cells. Polyclonal antibodies are produced by different clones of plasma B cells. Monoclonal antibodies interact with the same epitope in the antigen whereas polyclonal antibodies interact with the different epitopes of the same antigen. The main difference between monoclonal and polyclonal antibodies is the origin of the plasma B cells which produce antigens and the type of interactions of the antibodies.

Reference:

1. “MONOCLONAL ANTIBODIES.” Prospec, Available here.
2. “What is a polyclonal antibody?” How to make polyclonal antibodies, Available here.

Image Courtesy:

1. “Monoclonals” By Adenosine – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Biochem-polyclonal production” By Mei.huang at English Wikibooks (CC BY 3.0) via Commons Wikimedia