5.21B Describe the production of monoclonal antibodies, including: a use…

The idea

Monoclonal antibodies are identical antibodies made from a single cell line. The process starts with lymphocytes (a type of white blood cell) that produce the desired antibody, but these cells do not divide, so they cannot be grown in large numbers on their own. To solve this, a lymphocyte is fused with a tumour cell that can divide repeatedly, forming a hybridoma cell. The hybridoma combines both useful features: it produces the desired antibody and it divides, so it can be grown to make large quantities. As hybridoma cells divide, they keep producing the same antibody, giving a supply of identical (monoclonal) antibodies. A multiple-choice question may ask why lymphocytes are fused with tumour cells, or what a hybridoma cell does.

What earns the marks

• Lymphocytes produce the desired antibody but do not divide, so they cannot multiply on their own.
• A lymphocyte is fused with a tumour cell to form a hybridoma cell.
• The hybridoma cell can divide repeatedly, unlike the lymphocyte alone.
• Hybridoma cells produce the desired antibody as they divide, giving large quantities of identical antibodies.
• Monoclonal antibodies come from a single cloned cell line, so they are identical.

Common mistakes and how to put them right

• Thinking lymphocytes divide to make many antibody-producing cells.

  Put it right by stating lymphocytes produce antibodies but do not divide.

• Believing the tumour cell alone produces the desired antibody.

  Put it right by explaining the hybridoma, formed by fusing lymphocyte and tumour cell, produces the antibody.

• Assuming hybridoma cells stop producing antibody when they divide.

  Put it right by stating they produce antibody as they divide.

• Confusing monoclonal with many different antibodies.

  Put it right by noting monoclonal antibodies are identical, from one cell line.

Exam tips

• Remember the two features combined in a hybridoma: antibody production from the lymphocyte and division from the tumour cell.
• Use the term 'hybridoma' precisely; it is the fused cell, not either original cell.
• Check options for the reason lymphocytes alone are unsuitable: they do not divide.