C3.2 Defence against disease

Defence against disease combines physical barriers, clotting, phagocytes, lymphocyte specificity, vaccination, antibiotics and evolutionary responses to pathogens across human populations.

What you’ll learn

18 learning objectives

Choose one objective for a focused lesson, or study the complete topic.

Exam analysis

An aggregate view of how the complete C3.2 Defence against disease appears across past papers.

Chance of appearing47%of analysed past papers

Latest appearanceNovember 2025

Most common paperPaper1

Most tested objectives

C3.2.14—Antibiotic resistance evolution28 questions
C3.2.3—Blood clotting23 questions
C3.2.13—Antibiotics19 questions

Common question formats

Structured response
Definition or recall
Data analysis
Evaluation
Process explanation
Diagram interpretation
Extended response
Calculation

Exam question appearances

November 2025Paper2 ["HL"] · TZ18(c)[ 4 ]C3.2.12—HIV infection and AIDS

November 2025Paper1A ["HL"] · TZ326[ 1 ]C3.2.8—B-lymphocyte activation

November 2025Paper2 ["HL"] · TZ32(a)[ 2 ]C3.2.2—Skin and mucous membranes

November 2025Paper1A ["SL"] · TZ118[ 1 ]C3.2.15—Zoonoses

November 2025Paper1A ["SL"] · TZ117[ 1 ]C3.2.6—Lymphocytes

Practice this topic

8 original exam-style questions based on the patterns above.

Coverage 2010–2025 · Updated 16 Jul 2026