The Disadvantages of Polyclonal Antibodies

Polyclonal antibodies (PAbs), found naturally in the body, are used widely in disease therapy, as are monoclonal antibodies (MAbs). PAbs are useful in several ways, not least because they recognize multiple epitopes (a particular part of a protein). However, PAbs do have their disadvantages, such as their lack of consistency during production.

Homogeneity

• One of the main disadvantages with PAbs is their low homogeneity. It is the ability of antibodies to bind selectively with a specific epitope that makes them so useful and targetable in disease therapeutics, so if this is not a feature of a PAb, it actually represents a disadvantage. Low homogeneity means that PAbs do not bind to a variety of important molecules, including chemicals, carbohydrates, proteins and nucleic acids, which could have a detrimental impact on a wide range of different disease management processes.

Consistency and Reproducibility

• PAbs are less consistent and less reproducible than MAbs during laboratory, large-scale production. The reason for this inconsistency is that a sera created to contain a particular type of PAb will also contain antibodies that are different to the one required. Possible explanations as to the reason for the presence of another type of antibody in an animal's PAb sera include previous autoimmune responses and general immunological history. "Sera" (singular "serum") is a general term for the solution found in the body that contains dissolves antibodies and proteins. The immunological history of an animal includes the antibodies produced naturally to all the disease antigens and epitopes the animal has previously encountered.

Reduced Specificity

• Because PAbs can react with multiple epitopes they are considered, in some cases, less useful than MAbs. It is more difficult to evaluate changes in molecular conformation, protein-protein interactions and phosphorylation states using PAbs. Also, the process of identifying single members of protein families is limited when using PAbs rather than MAbs, as described by Neil S. Lipman, V.M.D., at the National Academy of Science.

Lack of Purity

• The concentration and purity levels of specific antibodies are up to 10 times lower in PAb sera than in MAb sera, typically between 50 and 200 micrograms per milliliter. PAbs form a much less pure serum, which is disadvantageous in treating disease because a much larger quantity is required to create a therapeutic effect. Low purity of PAbs means that vaccines using PAb sera are larger and more difficult to administer to patients.

Side Effects

• Polyclonal antibody treatments are associated with several deleterious side effects including a higher risk of infection from contaminating viruses, serum sickness and anaphylaxis (an acute immune hypersensitivity reaction), as explained by Surender Vaswani at the University of Utah.