Antibodies are indispensable in biomedical research. They are used, for example, in the diagnosis of infections or in research, such as for the localization of cells (immunohistochemistry). Even though more and more research is being conducted in vitro without animal testing, this does not, nowever, necessarily mean that material from animals is not being used.  “Fetal calf serum,” derived from blood, remains a common standard product in every cell culture laboratory—with all its drawbacks. But there are alternatives. (1) The same applies to antibodies used in research and diagnostics. (2)

To date, antibody production continues to focus primarily on the immunization of animals, even though the 2020 recommendations from the European Union Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM) highlight the scientific validity of antibodies of non-animal origin. (3) According to the recommendation, the provisions of Directive 2010/63/EU should be followed, under which EU countries should no longer authorize the development and production of antibodies through the immunization of animals unless there is a valid, legitimate scientific justification. (4)

In 2020, a fierce controversy erupted after ECVAM published its recommendation regarding the use of antibodies of non-animal origin. (4, 5) For example, some authors, such as Lutz, Gunzer et al. (2020), labelled the ECVAM publication as “industrial rabies lobbying disguised as animal welfare”; they claimed that the authors were “founders, board members, or employees of companies that produce antibodies from recombinant libraries or, for example, DARPINs.” (6)

In 2022, 184,830 animal experiments were documented in the EU and Norway for the routine production of monoclonal and polyclonal antibodies, along with an additional 49,309 registered animal experiments for the production of antibodies using the ascites method. (7) If such antibodies do not function as intended, incorrect scientific conclusions may be drawn, and studies may not be reproducible. There are therefore good reasons to switch to sequence-defined, recombinant antibodies and other non-animal-derived affinity reagents.

Phages—a Proven Alternative to Animals for Antibody Production
A phage library is a vast collection of bacteriophages, each of which presents a specific antibody fragment on its surface. The genetic material for the antibody fragments is derived from B lymphocytes, such as those from donors. mRNA is isolated from the B cells. cDNA is synthesized via reverse transcription, amplified by PCR, and cloned into phagemid vectors (specialized plasmids). The antibody fragment fuses with a phage coat protein and is thereby presented on the phage’s surface. The phages are amplified by bacteria that are infected with the phages and produce new phages. The bacteria thus produce the functional phage-antibody products. Only the appropriate phage type binds to the sample and can thus be identified; all other phages are washed away. Amplification, in turn, takes place in bacteria. (For the procedure, see, e.g., 8, 9, 10).

Low affinity? A misunderstanding
Today, there are high-quality antibody libraries with more than 10¹⁰ members, resulting in affinities in the subnanomolar range for antibodies obtained directly from the library. (3) Furthermore, antibodies from libraries are monovalent, whereas antibodies derived from immunization (typically of the IgG isotype) are bivalent. Additionally, the avidity of bivalent antibodies is often confused with affinity. This has led to the misconception that antibodies derived from phage display exhibit only low affinities. (Avidity refers to the total strength of the bond between a multivalent antibody and an antigen. It is often 10–100 times stronger than the affinity (single-binding strength)).

New Methods
The start-up Ymolution from Greifswald, Germany, on the other hand, produces its nanoantibodies using spores on the surface of bacteria. (11) The start-up Phaeosynt from Hannover produces its functional antibodies in diatoms. (12, 13) In this process, the blueprint (DNA) for specific antibodies is transferred into the algae, which then produce these proteins through photosynthesis while being cultivated in the laboratory. The startup was founded in 2023 and has gained recognition for its pregnancy test.

Sources and further information:
(1) Technical University of Berlin (2024). Liver tissue model produced entirely without materials of animal origin. Press release, May 7, 2024, wrt. https://www.tu.berlin/ueber-die-tu-berlin/profil/pressemitteilungen-hier-keine-neuen-unterordner-fuer-2025-anlegen-sondern-nur-noch-im-newsroom-arbeiten-unter-ordner-276490/ersatz-fuer-tierversuche-jetzt-ganz-ohne-tierleid
(2) Nordwig, H. (2025). Animal Blood for Antibody Tests—Medical Tests Without Animal Suffering. Tagesschau, Oct. 3, 2025. https://www.tagesschau.de/wissen/forschung/tierversuche-alternativen-100.html
(3) Cardone J, Knappik A. 20 Years of Providing Custom Non-Animal-Derived Antibodies—A Review. Altern Lab Anim. May 2025;53(3):168–174. doi: 10.1177/02611929251333981. Epub April 17, 2025. PMID: 40242979.
(4) EURL ECVAM (2020). Recommendation on Non-Animal-Derived Antibodies. https://publications.jrc.ec.europa.eu/repository/handle/JRC120199
(5) Bradbury ARM, Dübel S, Knappik A, Plückthun A. Animal-versus in vitro-derived antibodies: avoiding the extremes. MAbs. Jan–Dec 2021;13(1):1950265. doi: 10.1080/19420862.2021.1950265. PMID: 34281490; PMCID: PMC8293942. Bradbury ARM, Dübel S, Knappik A, Plückthun A. Animal-versus in vitro-derived antibodies: avoiding the extremes. MAbs. 2021 Jan–Dec;13(1):1950265. doi: 10.1080/19420862.2021.1950265. PMID: 34281490; PMCID: PMC8293942.
(6) Lutz, M., Gunzer, M., Dudziak, D., & Kamradt, T. (2020). Animal-derived antibodies remain indispensable in research
and clinical practice. Opinion. Trillium Immunology 2020; 4(4). DOI: https://doi.org/10.47184/ti.2020.04.07. https://www.trillium.de/zeitschriften/trillium-immunologie/archiv/heft-4/2020/aus-tieren-gewonnene-antikoerper-bleiben-unverzichtbar-in-forschung-und-klinik.html
(7) Lakjer, B. & Goddard Svendsen, R-. (2025). Implementing the EURL ECVAM Recommendation on Non-Animal-Derived Antibodies in One EU Member State — Denmark. Atla, Alternatives to Animal Research, Volume 53, Issue 2 https://doi.org/10.1177/02611929251324520
(8) Jülich Research Center, Institute for Biological Information Processes (IBI), Structural Biochemistry (IBI-7) (2022). Phage Display Selection. Online: https://www.fz-juelich.de/de/ibi/ibi-7/forschung/methoden/phagendisplay-selektion#:~:text=The%20presentation%20of%20peptides%20on,the%20DNA%20encoding%20them%20(genotype).
(9) Gabriel, M. (2008). Construction of a recombinant phage-display antibody library for the isolation of human monoclonal antibodies against Lassavirus and Plasmodium falciparum. Dissertation, Philipps University of Marburg, Institute of Virology. Online: https://archiv.ub.uni-marburg.de/diss/z2008/0296/pdf/dmg.pdf.
(10) Bionity.com (n.d.). Phage display. https://www.bionity.com/de/lexikon/Phagen-Display.html
(11) Laborjournal (2026). It All Comes Down to the Spore. https://www.laborjournal.de/editorials/3421.php
(12) Eilers, A. & Amrhein-Bläser, C. (2025). Wissen Hoch N. Antibodies from Diatoms—Vegan and Sustainable. Online: https://www.wissenhochn.de/en/themen/auswahl-und-uebersicht/einzelansicht/antikoerper-aus-kieselalgen-vegan-und-nachhaltig
(13) Phaeosynt (2026). Animal-free antibodies derived from diatoms. https://phaeosynt.com/