Explain how monoclonal antibodies are formed and suggest a potential use for monoclonal antibodies.

Monoclonal antibodies are antibodies that are produced by identical immune cell clones that only target one specific antigen. Monoclonal antibodies are produced after the target antigen is injected into an immunocompetent mouse. The mouse will naturally begin to produce lymphocytes, which can produce antibodies that can target the injected antigen. Spleen cells that produce these antigen-specific lymphocytes are surgically removed from the mouse. These spleen cells are fused with human myeloma cells (cancerous white blood cells) to form hybridoma cells. Hybridoma cells divide indefinitely and produce large quantities of antibodies that are all specific for one type of antigen. Monoclonal antibodies can be used in pregnancy tests, in which monoclonal antibodies against human chorionic gonadotropin (a hormone specifically produced after an embryo implants in the placenta of the mother) can detect the presence of the hormone in the urine of the mother. The hCG-monoclonal antibody complex can subsequently bind to a dye-tagged antibody that recognises the monoclonal antibody, so that the presence of the colour tag on the test indicates pregnancy.