Antibody Basics: Monoclonal, Polyclonal, and Recombinant Antibodies

Polyclonal vs Monoclonal vs Recombinant Antibodies

While simple in principle, antibodies are deceivingly complex in structure and to produce. There are key distinctions between polyclonal, monoclonal, and recombinant antibody production that are important to consider when designing a product. Let's take a closer look at the advantages and disadvantages these different antibody options could pose

Polyclonal → Monoclonal → Recombinant

Different Types of Antibodies

Polyclonal

Polyclonal antibodies are characterized by a pool of immunoglobulins that recognize multiple epitopes on a given antigen. Production of polyclonal antibodies begins with immunization of a host with an antigen of interest, followed by harvesting the resulting antibodies through blood draws. Separating leukocytes and erythrocytes from the whole blood yields antibody containing serum, which can be used directly in assays as antiserum. Antibodies can be further purified from antiserum through isolation of immunoglobulins by protein A or G purification, or via immunoaffinity purification for antigen-specific immunoglobulins.

Polyclonal antibodies are relatively inexpensive and quick to produce, and they bind with high avidity. This makes them ideal for laboratory tests requiring precipitation, such as immunoprecipitation (IP) and chromatin immunoprecipitation (ChIP), as well as other experiments such as western blots, immunohistochemistry, and fluorescence-activated cell sorting (flow cytometry).

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Monoclonal

Monoclonal antibodies are immunoglobulins that recognize one single epitope on a given antigen. The mouse is the common choice for sourcing monoclonal antibodies. Development begins with immunization of the mouse with an antigen of interest and the resulting immune cells are later harvested from the spleen. The spleen cells are then fused to an immortal myeloma cell line to create a hybridoma. After screening and stabilization to select the ideal clone, the hybridoma serves as a consistent long-term source of antibodies with lot-to-lot consistency that can be produced in vitro.

Monoclonal antibodies recognize a single epitope, with high specificity and reproducibility. They are particularly useful for projects requiring large amounts of antibody over a long period of time.

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Recombinant

Through the development and use of antibody engineering technology, many types of recombinant antibodies have become available. One type of recombinant antibody currently available is known as a Single Domain Antibody.

The Single Domain Antibody, VHH antibody, or nanobody, is a recombinant monoclonal antibody derived from camelids (llama, alpaca, camel, etc.). These nanobodies are the antigen-binding fragments of heavy chain only antibodies produced by these species.

After immunization, peripheral blood mononuclear cells are collected, their RNA isolated and used to construct a cDNA phage-display library containing sequences of antigen-specific binding fragments. The library is panned and screened to select high affinity binding antibody fragments. These fragments are then sequenced and expressed recombinantly.

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