Question

What are the pros and cons of using monoclonal antibodies vs polyclonal antibodies?

If you had a protein expressed at low levels that you were trying to isolate, which would you use?

Answer 1

Monoclonal Antibodies: These are antibodies that detect a single epitope of an antigen. They are produced by Hybridoma technology where an antibody producing B cell from spleen of immunized animal is fused with a myeloma cell line, leading to production of larger number of these antibodies.

Pros (Advantages)	Cons (Disadvantages)
Large number of these identical antibodies can be produced as cell lines are used.	Monoclonal antibody production takes longer time of around 6-9 months.
These antibodies produced show no variations as they are produced by the cell line. They are homogenous antibodies.	As they react only to a single epitope, their detection efficiency is low. Even small changes in epitope make these antibodies ineffective. Hence, they cannot be used for hemagglutination assay involving cross-linking of antigens. Multiple monoclonal antibodies are used for these applications, making them costly to use.
The antigen used for immunization does not need to be pure.	Hybridoma technology is expensive technique to use, requiring specialized personnel.
The clones that produce the specific antibody can be selected from the different clones using ELISA.	The fusion process may or may not form the right clone. There is 99% chance that the right clone is not produced in fusion process.
They are highly specific to the antigen they detect and thus, will not give much non-specific reaction. They are also highly sensitive to pH and salt changes and can be used to test for cross-reactivity.	Only mouse, rat and rabbit monoclonal antibodies have been produced. Small peptides cannot be used as immunogens.

Polyclonal Antibodies: Polyclonal antibodies are produced by simply immunizing the animals with the complete antigens and purifying them from the serum of the immunized animal. These antibodies recognize different epitopes of the same antigen.

Pros (Advantages)	Cons (Disadvantages)
As antibodies are directly obtained from sera, their production is faster and is less expensive. Antibodies can be produced in 2-3 months.	Specificity is lower as there is a higher chance of detecting non –specific antigen that may be similar. This may lead to detection of false positive reaction.
Different types of animals can be used to produce these antibodies. Polyclonal antibodies have been produced in horse, donkey, humans, rats, mouse, rabbit, guinea pigs etc.	Antibodies cannot be produced in the animal for a long time due to lifespan of the animal. Hence, large number of animals, probably with multiple immunizations is required to produce these antibodies.
Due to recognition of multiple antigenic epitopes, detection efficiency and sensitivity is higher.	Production of the antibody depends on the immune response generated by the antigen. Batch to batch variations will be observed.
Simple chromatographic techniques will purify these antibodies from sera.	Non-specific antibodies can be produced in the immunized antigens which may contaminate the final preparation.
They can be used for sandwich ELISA as they can easily capture the antigen of target protein.
Native protein can be easily detected by polyclonal antibodies.

Which Antibody to be used for low expressed proteins:

The polyclonal antibodies contain a heterogeneous mixture of antibodies that detect multiple epitope of the same antigen. Hence, they will be able to detect even low amounts of target protein. The lowly expressed protein will be able to bind to different antibodies in the polyclonal antibody mixture, thereby increasing its detection. Monoclonal antibody only recognizes a single epitope. This decreases its efficiency in detecting low target protein expression as the detection depends on the ability of the antibody to recognize low amount of epitopes.

Right choice: Polyclonal antibodies.