Introduction to Monoclonal Antibodies.

 

Introduction.

  • An antibody is a protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. 

  • Each antibody recognizes a specific antigen unique to its target. 

  • The high specificity of antibodies makes them an excellent tool for detecting and quantifying a broad array of targets, from drugs to serum proteins to microorganisms. 

  • With in-vitro assays, antibodies can be used to precipitate soluble antigens, agglutinate (clump) cells, opsonize (make more susceptible) and kill bacteria and neutralize drugs, toxins, and viruses. 

History and Development:

  • Paul Enrlich coined the term "magic bullets" at the beginning of the twentieth century, and proposed that this magic bullet would only harm disease-causing organisms while having no effect on normal host cells. 

  • Kohler and Milstein demonstrated the most outstanding proof of the clonal selection theory by fusing normal and malignant cells (Hybridoma technology) in 1975, for which they were awarded the Nobel Prize in 1984. 

  • The FDA approved the first monoclonal antibody in 1986. 

  • OKT3 orthoclone (muromonab-CD3), which has been approved for the prevention of kidney transplant rejection. 

    • Monoclonal antibodies (mAB) are identical antibodies directed against a specific epitope (antigen, antigenic determinant) and produced by B-cell clones derived from a single parent or hybridoma cell line.  

    • The fusion of one B-cell lymphocyte with a myeloma cell results in the formation of a hybridoma cell line.

    • Some myeloma cells naturally produce single mAB antibodies. 

Advantages of Monoclonal antibodies: 

  1. Despite its high cost, mAB is less expensive to develop than conventional drugs because it is based on proven technology.

  2. Side effects can be treated and reduced by using mice-human hybrid cells or antibody fractions.

  3. They bind to diseased or damaged cells that require treatment.

  4. They treat a wide range of ailments. 

Disadvantages of Monoclonal antibodies: 

  1. It is a time-consuming method that takes 6-9 months on average.

  2. It is very expensive and requires a lot of effort to make them.

  3. Small peptide and fragment antigens may not be suitable antigens because monoclonal antibodies may fail to recognize the original antigen.

  4. Hybridoma culture may become contaminated.

  5. The system is only well developed for a small number of animals and not for others.

  6. During the fusion process, more than 99% of the cells die, limiting the number of useful antibodies that can be produced against an antigen.

  7. Immunogenicity has the potential to be generated. 

Application of monoclonal antibodies:

  1. 1. Diagnostic Applications: 

    1. Monoclonal antibodies are very useful in  the laboratory diagnosis of various diseases. 

    2. MAbs in Biochemical Analysis: 

      1. Diagnostic tests based on the use of MAbs as reagents are routinely used in radioimmunoassay (RIA) and enzyme-linked immunosorbent assays (ELISA) in the laboratory. 

      2. These assays measure the circulating concentrations of various hormones, and several other tissue and cell products (like blood group antigens, blood clotting factors, interferon’s, interleukins, histocompatibility antigens, and tumor markers). 

  2. Pregnancy: 

    1. By detecting the urinary levels of human chorionic gonadotropin. 

  3. Cancers: 

    1. Cancers estimation of plasma carcinoembryonic antigen in colorectal cancer, and prostate specific antigen for prostate cancer. 

  4. Hormonal disorders: 

    1. Hormonal disorders analysis of thyroxine, triiodothyronine and thyroid stimulating hormone for thyroid disorders. 

  5. Infectious diseases: 

    1. Infectious diseases by detecting the circulatory levels of antigens specific to the infectious agent e.g., antigens of Neisseria gonorrhea and herpes simplex virus for the diagnosis of STDs. 

1.2 MAbs in Diagnostic Imaging: 

  1. Radiolabeled—

    1. MAbs are used in the diagnostic imaging of diseases, and this technique is referred to as immunoscintigraphy. 

    2. The radioisotopes commonly used for labeling MAb are iodine—131 and technetium—99. 

    3. The MAb tagged with radioisotope are injected 

    4. intravenously into the patients. 

    5. These MAbs localize at specific sites (say a tumor) which can be detected by imaging the radioactivity.

  2. Monoclonal antibodies are successfully used in the diagnostic imaging of cardiovascular diseases, cancers and sites of bacterial infections. 

1.3 Therapeutic Applications: 

  1. Cardiovascular diseases: Myocardial infarction: 

  2. Deep vein thrombosis (DVT): 

    1. DVT refers to the formation of blood clots (thrombus) within the blood veins, primarily in the lower extremities. 

    2. For the detection of DVT, radioisotope labeled MAb directed against fibrin or platelets can be used. 

    3. MAbs are successfully used for the detection of clots in thigh, pelvis, calf and knee regions. 

  3. Atherosclerosis: 

    1. The thickening and loss of elasticity of arterial walls are referred to as atherosclerosis. 

    2. Atherosclerotic plaques cause diseases of coronary and peripheral arteries. 

    3. Atherosclerosis has been implicated in the development of heart diseases. 

    4. MAb tagged with a radiolabel directed against activated platelets can be used to localize the atherosclerotic lesions by imaging technique.

Commonly Asked Questions.

  1. Write a short note on MOnooclonal Antibodies.

  2. Give applications of Monoclonal Antibodies.

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