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C3.2.9—Clones of plasma cells

Clones of plasma cells explains how a specific barrier, pathogen interaction, immune mechanism or treatment response contributes to protection against infectious disease.

Syllabus
First assessment 2025
Objective
C3.2.9
Level
SL

Plasma cells are antibody factories made by clonal selection

Because only a small number of B cells recognize a given antigen, an activated B cell divides repeatedly by mitosis to form a large clone.

Clonal expansion supplies enough plasma cells to secrete an effective quantity of one antibody type. Every plasma cell in the clone inherits the selected antibody specificity.

Rare matching B cell → activation → repeated mitosis → clone of genetically matching cells → many plasma cells secrete the same specific antibody; some cells can become memory cells.

A selected B cell responding to a bacterial surface antigen produces thousands of plasma-cell descendants, all releasing antibodies complementary to that antigen.

Antibodies are secreted in quantity by differentiated plasma cells, not by every inactive B cell. Mitosis increases cell number without changing specificity.

Clones of plasma cells

Assessment in practice

1 marks
How it is assessed

This objective is assessed through multiple choice, commonly using Identify / State.

Command terms

Identify / State

What earns marks

Mark schemes repeatedly reward named details, correct sequence and clear distinctions between similar processes.

Watch for

Confusing plasma cells, memory cells and helper T-cells in the activation sequence.

Representative question

Question 1

[Maximum number: 1]

What is a role of activated B cells?

A

Secrete antibiotics in response to specific antigens

B

Activate T cells in the immune response

C

Release histamine in response to allergens

D

Multiply to form clones of plasma cells

Defence Against Disease

  • Skin, mucus, cilia, lysozyme and clotting form primary barriers against pathogens.
  • Innate immunity is rapid and broad: phagocytes recognize, engulf and digest pathogens. Adaptive immunity is antigen-specific and forms memory.
  • Helper T-cells coordinate responses; activated B-cells undergo clonal selection, producing antibody-secreting plasma cells and memory cells. A second exposure therefore triggers a faster, stronger response.
  • HIV infects CD4 helper T-cells; their loss weakens immune coordination and can lead to AIDS.
  • Antibiotics target bacterial processes, not viruses. Antibiotic exposure selects resistant variants, which can spread by reproduction or plasmid transfer.
  • Vaccination creates active artificial immunity; high population immunity can indirectly protect susceptible people.
  • Evaluate disease and vaccine claims using reliable sources, trends, controlled comparisons, incidence and efficacy—not raw totals alone.

Concept essentials

  • Clones of plasma cells has to be linked to the exact pathogen, cell, molecule or population process involved.
  • The biological effect of clones of plasma cells depends on the sequence from trigger to protective outcome.
  • Clear distinctions within clones of plasma cells prevent confusion with neighbouring immune responses.
  • Evidence for clones of plasma cells is strongest when mechanism and consequence are explained together.