Applications for Animal Cell Lines
Introduction and Overview
Over several decades, mammalian cell lines have found profound use in the diverse fields of the life sciences. They have played an invaluable role in the advancement of the life sciences. Animal cell cultures were indispensable to the discovery and commercial production of several endogenous hormones such as insulin and several growth factors (Kokate, Pramod and Jalalpure 2012). Moreover, the understanding of normal physiological functions of the body heavily depended upon cell cultures. In more recent times, the importance of animal cell lines has become increasingly apparent in the monoclonal antibody production, cytokines, and various other protein biopharmaceuticals. New strategies for vaccine production also heavily hinge on cell culture techniques.
The monoclonal antibody production has been one of the most recent and most significant uses to which animal cell lines have been put. Pioneered in 1975, monoclonal antibody production has been ongoing for almost four decades now (Hale 2006). Monoclonal antibodies have a wide range of commercial, medical, and academic uses. They are used in numerous diagnostic tests in order to detect trace amounts of toxins, drugs, and hormones. This has been put to use in the detection of AIDS via the ELISA test. They have also been used in the treatment of viral diseases, which have for a long time been regarded as untreatable. Moreover, monoclonal antibodies have also found use in the classification of different strains of a single pathogen.
Mammalian cell lines have also been used in the production of other protein biopharmaceuticals. The cell lines most frequently used for this purpose are myeloma, hybridoma, and Chinese Hamster Ovary cells (Ferrer-Miralles et al. 2009). The biopharmaceuticals that have been produced by the use of different mammalian cell lines include blood factors XIII and IX, thrombolytic agents, haemopoietic growth factors, and interferons. Biopharmaceuticals produced from animal cell lines have several clinical, research as well as educational uses. Methods of producing these biopharmaceuticals have consistently evolved to make the products purer and more effective.
The use of cell cultures to produce monoclonal antibodies in vitro has been one of the longest uses of cell culture lines. This is among the very few methods that are so far available for the in-vitro monoclonal antibody production (Schäfer and Burger 2012). Therefore, cell cultures hold this significant place in the field of immunology, and they have been priceless in the study and advancement of immunology.
How it is done
The monoclonal antibody production through cell cultures, as has been mentioned, began in the seventies. The method that was devised then by Cesar Milstein and George Kohler has been tried, tested, and refined over the years. However, the basic principles still hold.
In-vitro monoclonal antibody production involves a number of interrelated steps. First, the particular antibody, which is to be produced, needs to be identified. Next, the B lymphocyte that produces that particular antibody is isolated. Isolation of the particular antibody involves injecting the animal – say a mouse – with two doses of the antigen that stimulates the production of the particular antibody (Carven, Van Eenennaam and Dulos 2012). The first dose is the primer dose and the second one, given about 10 days later, is the booster dose. The B-lymphocyte that produces the particular antibody is then stimulated and it begins its antibody production.
Next, a sample of B lymphocytes is taken from the spleen and then added to a myeloma cell culture. The intention is to produce hybridomas – cells, which are formed when a B cell and a myeloma cell fuse (Yagami, Kato, Tsumoto and Tomita 2013). This fusion is facilitated by electroporation, a virus, or by polyethylene glycol.
The next step is to grow the hybridoma in a medium that selects only hybridomas between B cells and myeloma cells. An appropriate medium would be a hypoxanthine-aminopterine-thymine (HAT), in which the culture would only allow the growth of the desired hybridomas (Burns 2009).
There are complications that the producer would have to get his way around. First, the initial pool of B cells is heterogenous, and the hybridoma population does not, therefore, produce a single antibody. Secondly, a hybridoma cell is originally tetraploid. The extra chromosomes are, however, somehow lost during subsequent divisions. Therefore, before selecting the particular hybridoma that produces the desired antibody, a sodium-dodecyl sulfate – polyacrylamide gel electrophoresis (SDS-PAGE) is done and subsequently, screening is done. After ascertaining that a particular hybridoma is producing the desired antibody, it is cultured and monoclonal antibodies are harvested from it.
Benefits, Disadvantages, and Ethical Issues
Monoclonal antibodies are extremely beneficial to the field of human therapy. They are meant to target specific antigens, and this specificity confers them a degree of efficiency that is out of reach of most other drugs (Bianchi 2010). Other drugs may also attack normal body cells, but monoclonal antibodies only target specific antigens, and this enables them to leave innocent cells out of the immunologic response.
Another benefit of monoclonal antibodies is that they can be used to suppress the immune system in place of such drugs as glucocorticoids (Bianchi 2010). They have been used to dodge organ rejections after transplants. Glucocorticoids also serve the same purpose, but they present a wide variety of undesirable side-effects.
On the darker side, the use of these antibodies still presents huge health challenges that compromise their effectiveness. Despite the major advances in science, the antibodies used for human treatment are still harvested from mice cells. The human body naturally rejects these antibodies, limiting their life-span (Bianchi 2010). Moreover, the antibodies thus produced usually have some side effects, including fever and vomiting.
Despite their usefulness, there are several ethical issues surrounding the monoclonal antibody production. These arise from the fact that the mice that are used in their production are forced to endure severe pain during the production of these antibodies (Buchwalow and Böcker 2010). During production, the producers usually desire to produce an enhanced inflammatory reaction in the mice, and this causes them to use adjuvants. These adjuvants release antigens slowly over a long period of time, causing a protracted period of physical pain for the mice. Additionally, the spleen of these mice has to be extracted in order to harvest these antibodies. Ethical issues have been raised over the use of mice to perform these procedures. In some countries, some adjuvants have even been banned. Scientists are exploring the possibility of in-vitro monoclonal antibody production to circumvent this painful treatment of mice.
In the monoclonal antibody production, certain quality assurance protocols have to be observed by the producers. For each monoclonal antibody produced, there is an expected dose-response ratio that the antibody has to meet (New England Biolabs 2013). For example, a response of about 20% of the maximum signal is expected from a 1/10000 dilution of the ELISA assay. This is a quality assurance standard that has to be met by the producers of the antibody used in the ELISA. Another quality assurance modus operandi is that the monoclonal antibody must not be able to react with other undesired proteins. If it does, it is considered unfit for use.
Summary and Conclusion
The monoclonal antibody production is one of the most frequent uses to which animal cell lines have been put. Indeed, cell-culture-based monoclonal antibody production has been in use for close to four decades, and the resulting benefits have been immense.
So far, monoclonal antibodies that are produced for human use are produced from mice specimen. The mice are injected with adjuvants, which introduce antigens into the body of the mouse. The antigens stimulate the monoclonal antibody production by B cells. The spleen of the specimen is then removed and some of the B cells therein harvested for use in growing a culture. The cells are injected into a myeloma, forming a hybridoma. The hybridoma is then placed in a medium that allows for selective growth of the desired hybridoma. Once this is achieved, screening is done, the desired hybridoma is then cultured indefinitely, and antibodies are harvested from it.
There are several advantages of monoclonal antibodies as opposed to other conventional methods of treatment. For one, antibodies are highly selective in their targets. Therefore, they do not interfere with bystander cells. Secondly, they can be used in the suppression of an individual’s immune system in cases of a transplant without any significant side effects. On the flipside, however, they sometimes produce mild clinical symptoms such as fever and vomiting.
There are a few ethical issues that also surround the production of antibodies by use of mice. The mice from which the antibodies are harvested endure protracted periods of pain and suffering, and this has been deemed unethical. Scientists are looking for other avenues of monoclonal antibody production that do not inflict harm upon the creatures.
Indeed, the life sciences have found a lot of use for animal cell lines. This could not be said any better for monoclonal antibodies. Before techniques to produce monoclonal antibodies through culture had been discovered, scientists groped in the dark about many things. However, with the monoclonal antibody production, several barriers to research and therapeutics have been surmounted with ever increasing prospects for better treatment. Indeed, the role that animal cell lines have played in the monoclonal antibody production cannot be overemphasized.