The Immune System

What The Immune System covers

The Immune System is examined in all three written papers — the specification states that Components 01, 02 and 03 can each assess content from any of the five modules, so nothing is confined to one paper. It covers primary defences and non-specific responses, B and T lymphocytes and the specific response, antibodies and testing for TB and HIV and types of immunity and allergy.

The 4 subtopics

Each one has its own page.

• Primary defences and non-specific responsesRecall questions on primary defences such as mucus, cilia, stomach acid and lysozyme, smoking and chest infections, inflammation, mast cells and histamine, neutrophils and macrophages, cytokines and opsonins, phagocytosis, and macrophages as antigen-presenting cells.Open →
• B and T lymphocytes and the specific responseRecall questions on where B and T lymphocytes are made and mature, clonal selection and expansion, plasma cells and memory cells, T helper, T killer and T regulatory cells, humoral and cell-mediated responses, and how the secondary response differs from the primary.Open →
• Antibodies and testing for TB and HIVRecall questions on antibody structure, variable and constant regions and the hinge, agglutination, antibody and antigen tests for HIV and the window period, testing babies of HIV-positive mothers, the Mantoux test and its limits, and interferon-gamma and urine antigen tests for tuberculosis.Open →
• Types of immunity and allergyRecall questions on natural and artificial, active and passive immunity with examples, why passive immunity is immediate but short-lived, antivenom, allergens and hypersensitivity, IgE, mast cells and histamine in hay fever, antihistamines, and anaphylaxis treated with adrenaline.Open →

What you need to know

Answer each one before you reveal it.

Take The Immune System further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Antigen vs Antibody

  Antigen: a foreign molecule, usually carried on the surface of a pathogen, that the immune system recognises as non-self and responds to. Antibody: a Y-shaped glycoprotein secreted by plasma cells, whose variable regions bind one specific foreign molecule.

• Opsonin vs Agglutinin

  Opsonin: a protein that coats the surface of a single pathogen so that phagocyte receptors can attach to it and engulf it far more readily. Agglutinin: a protein that binds two pathogens at once and so cross-links many of them into large clumps.

• T helper cell vs T killer cell

  T helper cell: a lymphocyte that binds antigen displayed on a presenting cell and releases cytokines to stimulate B lymphocytes and phagocytes. T killer cell: a lymphocyte that binds viral antigen on an infected body cell and releases perforin, making pores in its membrane so that it dies.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is a primary defence?

   Model answer

   A primary defence is a barrier that prevents pathogens entering the body in the first place, rather than dealing with them once they are inside.

2. 2

   How do mucus and cilia together protect the respiratory tract?

   Model answer

   Goblet cells secrete sticky mucus that traps pathogens and dust, and the cilia of the ciliated epithelium beat in a coordinated wave to sweep the mucus up to the throat, where it is swallowed.

3. 3

   What happens to pathogens that are swept up in mucus and swallowed?

   Model answer

   They pass into the stomach, where hydrochloric acid at about pH 2 denatures their enzymes and other proteins and kills them.

4. 4

   Name three secretions that contain lysozyme.

   Model answer

   Tears, saliva and mucus.

5. 5

   How does lysozyme kill a bacterium?

   Model answer

   It hydrolyses the peptidoglycan of the bacterial cell wall, so the weakened wall can no longer resist the entry of water by osmosis and the cell bursts.

6. 6

   Why is a smoker more likely to develop a chest infection?

   Model answer

   Tar in tobacco smoke paralyses and destroys the cilia, so mucus and the pathogens trapped in it collect in the airways instead of being swept out.

What is inside Levo

Six ways to work the same material.

The Immune System revision questions

What does The Immune System cover in OCR A-Level Biology B?

4 subtopics: primary defences and non-specific responses, b and t lymphocytes and the specific response, antibodies and testing for tb and hiv and types of immunity and allergy. Each one has its own page with questions and model answers.

How is The Immune System organised?

By the OCR H422 specification, subtopic by subtopic, so it matches the order you are taught it in.