11.1.7 Monoclonal Antibodies

Introduction

• Monoclonal antibodies (Mabs) are artificially produced antibodies produced from a single B cell clone
• The hybridoma method is used to make monoclonal antibodies 
• The method enables large quantities of identical antibodies to be produced
• The hybridoma method solved the problem of having B cells that could divide by mitosis but not produce antibodies and plasma cells that could produce antibodies but not divide
• This method was established in the 1970s
• Monoclonal antibodies bind antigens, in the same way naturally produced antibodies

Creating Hybridoma cells

• Hybridoma cells are created by combining specific antibody producing B cells with myeloma (tumour) cells
• Plasma cells producing the required antibodies are created by injecting mice with the target antigen to trigger an immune response
• This results in plasma cells producing the required antibodies to complement the target antigen
• These plasma cells are removed from the spleen of the mouse before being fused with immortal myeloma cells cultured in the lab to make hybridoma cells
• Hybridoma cells producing the required monoclonal antibody can then be isolated and used in large scale monoclonal antibody production

• The hybrid cells produced using the hybridoma method above, are grown in a selective growth medium
• A mix of hybridoma cells producing several different types of antibody can then be screened to identify and isolate the hybridoma producing the desired antibody
• A culture of these hybridoma cells can then be encouraged to divide by mitosis in optimum conditions in a fermenter to produce identical clones all producing identical antibodies - monoclonal antibodies
• Monoclonal antibodies are complementary to the original antigen injected into the mouse initially
• Monoclonal antibodies have multiple applications to include the diagnosis of many different diseases such as HIV, malaria, COVID-19, or even the treatment of diseases such as rabies
• Additionally, they may be used in food safety testing and pregnancy testing

• Urine samples can be used in pregnancy testing
• Pregnancy testing sticks contain monoclonal antibody molecules that are specific to a hormone produced during pregnancy (that therefore becomes present in the mother's urine)
  • This hormone is human chorionic gonadotropin (hCG), which is secreted by the early embryo after it has implanted in the uterus
  • The antibodies in the testing sticks all originate from a single clone of B lymphocyte cells that all produce the same antibody specific to hCG
  • This minimises the chances of false test results

Monoclonal antibodies are used to detect the presence of the hormone hCG in the urine of pregnant women.