Monoclonal And Polyclonal Antibodies: Fill & Download for Free

Monoclonal antibodies are made using identical immune cells that are all clones of a specific parent cell. As such, they will have affinity for the same antigen and epitope (i.e. are monovalent).Polyclonal antibodies are made using several different immune cells. They will have affinity for the same antigen but different epitopes.Here's the same info in image form:Monoclonal and Polyclonal Antibody Binding.Monoclonal antibodies bind only a single epitope while polyclonal antibodies bind different epitopes on the same protein.Image and legend from Primary Antibody Selection & OptimizationWhich is better?Monoclonal antibodies are much more specific and with less background noise than polyclonal antibodies, and are as such generally preferable for biochemical assays. However, they are also usually more expensive to produce, less robust and are very sensitive to small changes in the antigen.

The difference lies primarily in how monoclonal and polyclonal antibodies are produced. Polyclonal antibodies are generated by exposing an animal to an antigen of interest (usually by injection), which triggers an immune response and the production of many different antibodies that target the introduced antigen. The antibodies are harvested by collecting the blood of the animal exposed to the antigen and purifying the serum away from other blood components.Monoclonal antibodies are produced by generating a cell line from the fusion of an antibody producing cell with an immortalized cell type. Since each antibody producing cell only makes one type of antibody, the generated cell line will only make a monoclonal antibody. The immortalized cell line can be passaged and expanded indefinitely, so you can keep producing the same antibody. In contrast, you can only collect the blood of an immunized animal once, so polyclonal antisera are unique.Polyclonal antibodies are generally WAY more sensitive per microgram of antibody than monoclonals, because they're capable of recognizing many different sites on the antigen of interest. Unfortunately, this can also lead to significantly more background if the antiserum hasn't been appropriately purified. On the other hand, monoclonal antibodies are much easier to characterize and are thus way more predictable. For medical diagnostic approaches (like pregnancy tests), predictability and specificity is much, much more important than sensitivity, so monoclonals are preferred. For something like an immunopurification or immunofluorescence, the added sensitivity often makes sense because you may be trying to detect low abundance antigens.Monoclonals are generally preferred for industrial applications, because you can keep making monoclonals for as long as you have the cell line, while the supply of a polyclonal antibody is limited to the serum generated from the final bleed of your immunized animal.Generating monoclonal antibody lines is very time consuming and expensive, so it usually only makes sense if there are going to be a lot of users of that antibody. For custom antibodies, generating polyclonal antisera is much faster.

Some definitions first for a general audiencePolyclonal antibodies - Wikipedia: Usually the serum product of an immunized animal. Heterogeneous because they compriseVarious antibodies specific for a variety of antigens, some specific for different epitopes of the same antigen,Different antibody classes and sub-classes, i.e., Isotype (immunology) - Wikipedia, andWide range of antibody concentrations (Antibody titer - Wikipedia) and affinities for their respective antigens.Monoclonal antibody - Wikipedia (mAbs): Products of a hybridoma clone (Hybridoma technology - Wikipedia), derived from a single antibody-secreting B cell fused to a myeloma cell line. Homogeneous. In essence, product of a cellular factory spewing out that one mAb. Thus, the secreted antibody is mono-specific, with a single affinity to the single epitope it binds on the antigen, and is of a single antibody class (Immunoglobulin class switching - Wikipedia).Epitope: Site that an antibody binds on an antigen.Affinity: Strength of antibody binding to antigen.Avidity: Sum of affinities of multiple antigen-binding sites on an antibody.Polyclonal antibodies: Pros & ConsUnlike mAbs, polyclonal antibodiesCan be produced faster and more cheaply.Can bind their target antigens under a variety of salt and pH concentrations so are more stable.Comprise antibodies specific for different epitopes of a given antigen. Outcome is higher antibody affinity, i.e., antigen-binding sensitivity.Easier to couple to a variety of labels such as enzymes, Fluorophore - Wikipedia, etc.Such attributes make polyclonal antibodies a better option in assaysFor binding proteins sensitive to conformational changes or denaturation, or which are polymorphic.In Immunoprecipitation - Wikipedia (IP) and Chromatin immunoprecipitation - Wikipedia (ChIP) assays.For detecting low concentrations of a given protein.As capture antibody in sandwich ELISA - Wikipedia (Enzyme-Linked Immunosorbent Assay), one of the most widely used assays to detect and quantify antigens. For capture and not for detection. ELISA assays using them for detection are more susceptible to dramatic changes when diluting sera since a polyclonal serum contains varying antigen specificities and affinities at different concentrations (titers). OTOH, diluting mAbs doesn't affect their affinity/avidity so easier to interpret that a change in reaction results from change in antigen concentration. While mAbs have a single specificity, heterogeneity of polyclonal antibodies means varying affinities even against the same epitope which makes assessing their specificity much more complicated. Unlike polyclonal antibodies, using mAbs for detection in ELISAs allows calibration, and therefore, standardization.However, major drawbacks of polyclonal antibodies areBatch-to-batch variability since each batch is typically product of one or few immunized animals. OTOH, being products of immortalized cells, practically limitless amounts of mAbs can be produced.Binding multiple epitopes on a given antigen increases scope for cross-reactivity. This necessitates affinity purification (Affinity chromatography - Wikipedia) before using them in assays.Consequence of polyclonal antibodies comprising different antigenic specificities and affinities is higher background signal in various assays, i.e., lower specificity.Some Therapeutic Applications of Polyclonal antibodiesPolyclonal antibodies are widely used for Immunosuppression - Wikipedia to prevent acute rejection in transplant recipients. In transplants, one of the major logistical problems is severe, chronic shortage of living donors. As a result, criteria have steadily expanded to include organs previously precluded from consideration. These include greater tissue mismatches, and organ and tissue donations after cardiac death. Problem with using expanded criteria organs is higher probability of rejection. This necessitates using more powerful immunosuppressive therapy, often lifelong.Some polyclonal antibody preparations have become mainstays among immunosuppressive regimens used to prevent early, acute rejection in solid organ transplants. Two main types of polyclonal antibody preparations are widely used, one sourced from rabbits, the other from horses (Anti-thymocyte globulin - Wikipedia). They are (1, 2, 3, 4, 5, 6)Thymoglobulin®, a rabbit anthymocyte globulin (rATG).ATG-Fresenius, a rabbit anthymocyte globulin.ATGAM® or eATG, equine antithymocyte globulin.Lymphoglobulin®, horse ATG.Thymoglobulin®, a rabbit anthymocyte globulin (rATG)First licensed in April 1984 in Europe and in 1999 in USA (6).Manufactured by Genzyme/Sanofi.Is polyclonal IgG anti-human thymocyte globulin.Rabbits are immunized with human Thymocyte - Wikipedia (developing T cells).Is widely used in solid organ transplants.Was given to ~ half of all new kidney transplant recipients in the US between 2000 and 2009 (7).Initially used in kidney transplants, today it's used in a variety of solid organ transplants such as liver, heart, lung, pancreas, intestinal as well as hematopoietic stem cell transplantation and aplastic anemia (1, 5).ATG-FreseniusManufactured by Neovii Biotech (formerly Fresenius Biotech) (4).Rabbits are immunized with a human Jurkat cells - Wikipedia line.ATGAM® or eATG, equine antithymocyte globulin (5)Horses are immunized with human T cells and their antibodies harvested from their serum.Developed by Peter Medawar - Wikipedia in the 1950s.Thomas Starzl - Wikipedia started using it in the 1960s.Registered for use in kidney transplantation in the US since 1981.First commercially available ATG in Europe and USA.Manufactured by Pfizer (previously Pharmacia Upjohn).Lymphoglobulin®, Horse ATGManufactured by Genzyme/Sanofi.To avoid early, acute rejection, high-risk transplant recipients, usually defined as glucocorticoid-resistant, are typically given these antibodies starting shortly before the transplant and continuing immediately afterward for a few weeks.While exact mechanism by which these complex reagents immunosuppress is unknown, ADCC (Antibody-dependent cell-mediated cytotoxicity - Wikipedia) likely causes rapid and widespead lysis of T cells though elimination of other cells such as NK cells is also possible. This Rx also entails serious risks which include Cytokine release syndrome - Wikipedia, Thrombocytopenia - Wikipedia, Leukopenia - Wikipedia, higher infection risk, and many others (2, 3, 4, 5, 8, 9).Bibliography1. Gaber, A. Osama, et al. "Rabbit antithymocyte globulin (thymoglobulin): 25 years and new frontiers in solid organ transplantation and haematology." Drugs 70.6 (2010): 691-732. https://www.researchgate.net/profile/Yvon_Lebranchu/publication/43159002_Rabbit_Antithymocyte_Globulin_ThymoglobulinR/links/0fcfd50e6a7b729c96000000.pdf2. Penninga, Luit. Immunosuppressive Polyclonal and Monoclonal T-cell Antibody Induction Therapy for Solid Organ Transplant Recipients: Systematic Reviews with Meta-analyses and Trial Sequential Analyses of Randomised Clinical Trials: Ph. D. Thesis. Afsnit 7812, Blegdamsvej 9, 2100 Ø, 2014. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.701.1181&rep=rep1&type=pdf3. Chen, Huifang, Qian, Shiguang. "Current Immunosuppressive Therapy in Organ Transplantation." CURRENT IMMUNOSUPPRESSIVE THERAPY IN ORGAN TRANSPLANTATION: 51. https://www.researchgate.net/profile/James_Mcdaid/publication/282134673_Current_Immunosuppressive_Therapy_in_Organ_Transplant/links/56045c5f08ae8e08c08a720e.pdf#page=654. Nishihori, Taiga, et al. "Antithymocyte globulin in allogeneic hematopoietic cell transplantation: benefits and limitations." Immunotherapy 8.4 (2016): 435-447.5. https://www.fda.gov/downloads/ApprovedProducts/UCM199603.pdf6. Thymoglobulin7. Cai, J., and P. I. Terasaki. "The current trend of induction and maintenance treatment in patient of different PRA levels: a report on OPTN/UNOS Kidney Transplant Registry data." Clinical transplants (2009): 45-52.8. Bamoulid, Jamal, et al. "Anti-thymocyte globulins in kidney transplantation: focus on current indications and long-term immunological side effects." Nephrology Dialysis Transplantation (2016): gfw368.)9. Malvezzi, Paolo, Thomas Jouve, and Lionel Rostaing. "Induction by anti-thymocyte globulins in kidney transplantation: a review of the literature and current usage." Journal of nephropathology 4.4 (2015): 110. https://www.researchgate.net/profile/Thomas_Jouve/publication/282812111_Induction_by_anti-thymocyte_globulins_in_kidney_transplantation_A_review_of_the_literature_and_current_usage/links/56430d0308aeacfd8938a88c.pdfThanks for the R2A, Anonymous.