Antibodies function in basic research, as diagnostics, and as sophisticated therapeutics.

Introduction 

• Antibodies are a proteins part of the body's immune response to antigens, which are foreign elements or viruses that trigger an immune response. They are proteins comprised of two heavy chains and two light chains which are held together by sulphide bridges. The variable region is the site of antigen interaction that consists of the paratope and binds the epitope of an antigen. Antibodies can be used to locate and identify specific proteins. They are also used to identify disease-related targets, and to select, optimise, and develop candidate drugs.  

Antibodies in Research 

• Chromatin immunoprecipitation assays, or ChIP assays, can be used evaluate the regulation of molecular pathways and better understand gene function in both healthy and disease tissues and study gene expression. For the best results, ChIP antibodies should be well characterised, proven to bind to its target protein, rigorously tested for specificity, and ideally validated in ChIP. Protein-nucleic acid interactions are a key factor in predicting the function of antibodies. Antibodies are classified into five major classes: IgA, IgD, IgE, IgG, and IgM each with different function and antigen response. For example, IgG is the main antibody in blood and can bind to bacteria and toxins. 

• Protein localisation is the process of moving proteins to and maintaining them in specific locations within a cell. It is a mechanism that regulates cellular functions. Immunofluorescence and immunohistochemistry are methods that use antibodies for detection and localization of proteins and other antigens within biological samples.  Antibodies are chemically conjugated to fluorescent dyes and then used to bind to antigens in a sample. The sample is then exposed to short-wavelength light, which is absorbed and re-emitted as light of a longer wavelength. This emitted fluorescence can be visualized using a microscope.  

• Antibodies are useful in toxicology, where they are employed to detect drugs. Immunoassays are a bioanalytical method that uses antibodies or antigens to measure the presence or concentration of analytes in a solution. Immunoassays are highly specific because they use purified antibodies and antigens. Immunosensors are used to detect the immunochemical reaction between antigens and antibodies. They can detect the presence of antibodies and are used as a diagnostic indication for toxic substances. Antibodies are widely used to localise proteins, but they are less common than transgenic reporter experiments in some cases. This is because antibodies can be difficult to scale for high-throughput localization studies. 

Antibodies in Diagnostics and Therapeutics 

• Antibody serology tests are diagnostic tools that detect the presence of antibodies in the blood. These antibodies are proteins produced by the immune system in response to infections, vaccinations, or autoimmune reactions. They can be used to detect immune response. When the body encounters a pathogen, it produces antibodies that can specifically recognize and neutralize that pathogen. Antibody serology tests can detect these antibodies to determine if a person has been exposed to a virus, bacteria, or other pathogens, even if they are not currently infected. For diseases like COVID-19, tests can indicate past infection or vaccination status. 

• In autoimmune diseases like type 1 diabetes, the immune system mistakenly attacks the body’s own tissues. Antibody serology tests can identify autoantibodies such as islet autoantibodies that target the body’s own cells, to help diagnose the disease. Teplizumab is a monoclonal antibody approved by the FDA in November 2022 for to delay the onset of type 1 diabetes in patients aged 8 and older. The antibodies are delivered through a daily infusion for 12 days. It modifies T cells by binding to CD3 to prolong the pancreas' ability to create insulin works. It is the first drug to delay the progression of an autoimmune disease before clinical onset. Side effects include headaches, gastrointestinal symptoms, rashes, and a decrease in white blood cells. 

The ELISA test 

• Antibodies are used to identify, collect, and purify specific proteins from a mixture. This is crucial for studying protein functions, structure, and interactions. For example, monoclonal antibodies, antibodies produced in a lab from a single antibody, are used in techniques to identify proteins based on their antigen-antibody binding. An enzyme-linked immunosorbent assay, or ELISA, is a serological test can be used to diagnose a variety of conditions. ELISA measures antibodies in the fluids such as blood, urine, semen and oral fluid, which is the mixed saliva from the glands and other constituents present in the mouth. It can help diagnose bacterial and viral infections such as HIV and Lyme disease and endocrine conditions like thyroid disease. 

• The test requires two key elements: adsorption of antibody or antigen to a solid surface; and an enzyme-linked antibody. If the sample contains the antibody being tested for, the enzymes on the plate will attach to it and cause the plate to change colour. The most common HIV tests use antibodies from a patient's blood sample to detect HIV infection. Oral fluid collected from the cheeks and gums may also be used to perform an ELISA, as they are considered as sensitive as a blood test. A urine sample may also be used during an ELISA, but this is considered less accurate than a blood or oral fluid test. A positive ELISA for all samples must be used with a confirmatory test, such as the Western blot test, to make a positive diagnosis. Although false negative or false positive results are extremely rare, they may occur if the patient has not yet developed antibodies to HIV or if a mistake was made at the laboratory. 

Conclusion 

• In summary, antibodies are powerful tools in medical diagnostics and research. The unique structure of antibodies allows for specific binding to antigens. Because of this, they play a key role in identifying infections, autoimmune diseases, and toxic exposures, as well as purifying proteins for scientific study. Monoclonal antibodies have been used in diagnostics and therapeutics, and they have helped improve the treatment of major diseases.  Antibody therapeutics are becoming increasingly important in the pharmaceutical market, with new drugs being approved for treating a variety of diseases.