Immunity: Question 5

Worked solution

Step 1: Recall what “monoclonal” means

“Mono-” means one, and “clonal” refers to a clone: a population of genetically identical cells descended from a single original cell. A monoclonal antibody is therefore a large batch of identical antibody molecules, all with the same variable region and so all specific to one particular antigen.

Step 2: Recall how monoclonal antibodies are produced

To make monoclonal antibodies, a B-lymphocyte that produces the desired antibody is fused with a tumour (myeloma) cell. This fusion produces a hybridoma cell, which combines two useful properties: the B-lymphocyte’s ability to produce one specific antibody, and the tumour cell’s ability to divide repeatedly. The hybridoma cell is cloned to produce many identical cells, all secreting the same, single type of antibody in large quantities. This is very different from a normal immune response, in which many different B-lymphocytes are activated and produce a mixture of different antibodies (a polyclonal response).

Step 3: Evaluate each option

• A: incorrect. This describes a polyclonal mixture of antibodies, not monoclonal antibodies, which are all identical.
• B: correct. Monoclonal antibodies are identical antibodies produced from clones of a single hybridoma cell, so they are all specific to one antigen.
• C: incorrect. Monoclonal antibodies are produced using B-lymphocytes (fused with tumour cells), not T-killer cells, and antibodies act by binding to their target antigen rather than destroying cells unaided.
• D: incorrect. A patient’s natural antibody response is polyclonal (a mixture of different antibodies); monoclonal antibodies are manufactured from a single cloned cell line, not simply extracted from blood.

Final answer

• Monoclonal antibodies are identical antibodies produced from clones of a single hybridoma cell and are specific to one antigen, option B.