Yes, monoclonal antibodies can be used against viruses. They work by recognising and binding to specific proteins on the virus's surface, neutralising the virus's ability to infect host cells. This is particularly effective for viruses that have well-defined surface proteins accessible to antibodies. For example, Palivizumab is a monoclonal antibody used to prevent respiratory syncytial virus (RSV) infections in high-risk infants. It binds to a protein on the RSV surface, preventing the virus from entering cells. Similarly, in the treatment of COVID-19, monoclonal antibodies have been developed to bind to the spike protein of the SARS-CoV-2 virus, blocking its ability to infect human cells. These treatments are most effective when administered early in the infection, as they can directly neutralise the virus before it has a chance to replicate extensively.

In organ transplantation, monoclonal antibodies are used primarily to prevent organ rejection by the recipient's immune system. Rejection occurs when the immune system recognises the transplanted organ as foreign and attacks it. Monoclonal antibodies like Basiliximab and Daclizumab target and inhibit the activity of T lymphocytes, a key component of the immune system responsible for this rejection. By selectively suppressing T cell activity, these mAbs reduce the likelihood of acute rejection episodes without broadly suppressing the entire immune system, thereby minimising the risk of infections and other complications associated with general immunosuppression. Additionally, mAbs are used in the induction therapy, administered immediately before or after the transplant to provide a strong initial suppression of the immune system, helping the body to accept the new organ.

Despite their precision and effectiveness, monoclonal antibodies have several limitations in medical therapy. Firstly, their production is complex and expensive, making treatments costly and potentially inaccessible for some patients. Secondly, as foreign proteins, mAbs can sometimes trigger immune responses, leading to allergic reactions or the development of antibodies against the treatment, reducing its efficacy. Thirdly, mAbs are mostly administered intravenously, requiring hospital visits and making self-administration difficult. Another limitation is their inability to penetrate solid tumours effectively due to their large size. This restricts their use against certain types of cancer. Lastly, the specificity of mAbs can be a double-edged sword; if the target antigen mutates or is not present on all target cells, the treatment may not be effective against all cancer cells or may become less effective over time.

The development and use of monoclonal antibodies in research involve several ethical issues. One primary concern is the use of animals, particularly mice, in the production of hybridomas for generating monoclonal antibodies. This raises questions about animal welfare and the ethical justification of using animals for research purposes. There are also concerns about the transparency and reproducibility of research findings when proprietary monoclonal antibodies are used. Since these antibodies can be expensive and their exact composition is often a trade secret, it can be difficult for other researchers to replicate studies or verify results. Furthermore, the commercialisation of monoclonal antibodies has raised concerns about the prioritisation of profit over scientific value and healthcare equity. This includes issues such as the affordability of monoclonal antibody-based therapies and the allocation of research funding towards projects with commercial potential rather than those of purely scientific or public health interest.

Monoclonal antibodies (mAbs) and polyclonal antibodies are distinct in their production, specificity, and applications. mAbs are produced from a single clone of B cells and are therefore identical, targeting a specific epitope of an antigen. This homogeneity ensures high specificity and consistency, which is crucial in therapeutic applications and diagnostic tests like ELISA. In contrast, polyclonal antibodies are produced by different B cell clones in response to an antigen, resulting in a mixture of antibodies that target multiple epitopes on the same antigen. While polyclonal antibodies offer a broader range of antigen recognition, they lack the precision of mAbs and can lead to higher background noise in diagnostic tests. Their production is quicker and less costly than mAbs, making them useful in research settings for detecting antigens with multiple epitopes and in situations where high specificity is not critical.