Monoclonal Antibodies¶

Part of Infection and Response.

Monoclonal antibodies are useful because one cloned cell line makes one type of antibody, so every molecule binds to the same target. This makes them powerful tools for testing, imaging and treatment.

What You Need to Learn¶

Higher Tier: learn how cloned antibody-producing cells provide a supply of antibodies with the same target. Use that specificity to explain diagnostic tests, laboratory research and targeted treatments, while recognising why side effects limit their benefits.

Producing Monoclonal Antibodies¶

A mouse is first stimulated to produce lymphocytes that make a desired antibody. These lymphocytes are then fused with tumour cells to make hybridoma cells.
Hybridoma cells divide rapidly like tumour cells but keep the ability to make one specific antibody like the original lymphocyte.
Cloning the hybridoma produces large amounts of identical antibody, which can then be collected and purified.

Uses and Limits¶

Monoclonal antibodies can be linked to dyes or radioactive substances to locate specific molecules or cells in the body.
They are used in pregnancy tests, laboratory tests and some cancer treatments because they can be designed to bind to a chosen target.
Like any medical treatment, they can have side effects, so benefits have to be balanced against risks.

An antibody’s binding site fits a particular part of its antigen. In a pregnancy test, antibodies recognise a pregnancy-associated hormone; binding can produce a visible signal. Laboratory tests use the same matching principle to measure hormones or detect pathogens. A fluorescent label lets researchers locate a target molecule in a cell or tissue.

For cancer treatment, an antibody can carry a radioactive substance, toxic drug or growth-blocking chemical to cells bearing its target antigen. This aims to reduce damage to other cells, but targeting is not a guarantee of no harm. Unexpected side effects have limited some uses, so assess the benefit and risk rather than assuming specificity makes a treatment harmless.

Common Confusions¶

Monoclonal vs. polyclonal antibodies: Monoclonal comes from one cell clone and targets one epitope (one specific part of an antigen). Polyclonal (from natural immune response) includes many different antibodies targeting different parts of the same antigen.
Why fuse with tumour cells: Normal lymphocytes can make antibodies but divide only a few times. Tumour cells divide forever but don't make antibodies. Hybridomas combine both abilities.
Cloning: Making clones of hybridoma cells produces identical cells that make identical antibody. This is cloning of cells, not cloning of whole organisms.

Key Terms¶

Monoclonal antibody: an antibody produced from a single clone of cells and therefore all identical.
Polyclonal antibody: a mixture of different antibodies, each targeting different parts of an antigen.
Hybridoma: a cell formed by fusing a lymphocyte with a tumour cell.
Lymphocyte: a type of white blood cell that produces antibodies.
Specificity: the property of binding to one particular target and not others.
Antigen: a molecule recognised by the immune system as foreign or targetable.
Epitope: a specific part of an antigen that an antibody binds to.
Pregnancy test: a test that uses monoclonal antibodies to detect a hormone (hCG) linked to pregnancy.