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C3.2.10—Immunity from memory cells

Immunity from memory cells explains how a specific barrier, pathogen interaction, immune mechanism or treatment response contributes to protection against infectious disease.

Syllabus
First assessment 2025
Objective
C3.2.10
Level
HL

Exam analysis

Chance of appearing3%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper2
Typical marks1–3

Common command terms

  • State
  • Suggest
  • Identify
  • Explain

Scoring notes

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

Recent exam appearances

May 2025Paper2 ["HL"] · TZ25(b)[ 2 ]C3.2.10—Immunity from memory cells
May 2021Paper1 ["HL"] · TZ237[ 1 ]C3.2.10—Immunity from memory cells
November 2019Paper2 ["HL"] · TZ01(f)(ii)[ 3 ]C3.2.10—Immunity from memory cells
Practice this objective

Coverage 2019–2025 · Updated 16 Jul 2026

Memory cells accelerate a second response

Memory cells accelerate a second response.

Some activated B and T cells persist as memory cells. On re-exposure they respond more rapidly and strongly, often preventing noticeable disease.

primary exposure; memory formation; secondary exposure; faster/larger response.

A booster vaccine re-stimulates memory cells, producing protective antibody levels sooner than the first dose.

Memory is antigen-specific and can weaken; it does not make a person immune to every pathogen.

Immunity from memory cells

Assessment in practice

1–3 marks
How it is assessed

This objective is assessed through structured response, commonly using State / Suggest / Identify.

Command terms

State / Suggest / Identify / Explain

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: 3]

Suggest possible reasons for the observed pattern of presence of antibodies in vaccinated mice.

The summer after vaccination, the prevalence of B. burgdorferi infection in tick nymphs collected on mice from the two sites was measured.

\cline { 2 - 5 } \multicolumn{1}{c|}{}State of infection of tick nymphs with B. burgdorferi
\cline { 2 - 5 } \multicolumn{1}{c|}{}Site 1Site 2
Host miceInfectedNot infectedInfectedNot infected
Control mice903155789
Vaccinated mice8728849121

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

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