11.2.1

Immune System

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Inducing the Immune Response

The immune system is made up of specialised cells that respond specifically to foreign objects and protect an individual from harm. The cells detect:

Pathogens

Pathogens

  • Pathogens are organisms that cause disease.
    • Most pathogens are micro-organisms (e.g. bacteria and viruses).
    • Some pathogens are fungi or protists.
Cells from other organisms

Cells from other organisms

  • Immune cells can detect the presence of cells from other organisms of the same species.
    • E.g. An organ transplant can induce an immune response.
Abnormal body cells

Abnormal body cells

  • Immune cells can detect the presence of cells in the body that are not functioning as normal.
    • E.g. Cancerous cells.
Toxins

Toxins

  • Toxins are harmful substances produced by pathogens.
  • Immune cells can detect the presence of toxins.

Antigens

The immune system responds to pathogens and other foreign bodies due to the presence of antigens.

'Foreign' signals

'Foreign' signals

  • Antigens are molecules (proteins and glycoproteins) that are present on the cell surface membrane of all cells.
  • Antigens signal to the immune system if the cells are 'foreign'.
Specificity

Specificity

  • Every cell has specific antigens.
  • The antigens bind to complementary receptors on the cell surface membrane of the immune cells.
  • If the antigens are 'foreign', this will induce an immune response.
'Self' signals

'Self' signals

  • Not all antigens induce an immune response.
  • Antigens can also signal if the cells are 'self' or they belong to the host organism.
Response

Response

  • The immune system can respond to antigens in a number of ways:
    • Lysozymes break down the foreign cells.
    • Phagocytosis of the foreign cells.
    • Production of antibodies that bind to the antigens and inhibit the functioning of the foreign cells.

Overview of the Immune Response

The immune response is the series of steps that are initiated when a foreign antigen is detected by the cells in the body. The steps are:

1) Phagocytosis

1) Phagocytosis

  • Pathogens are ingested by specialised cells called phagocytes.
    • Phagocytes are a type of white blood cell.
  • The pathogens are destroyed inside the phagocytes.
2) Activation of T cells

2) Activation of T cells

  • Phagocytes activate T lymphocyte cells (a type of white blood cell).
  • There are two types of T cells that respond in different ways:
    • Helper T cells (TH).
    • Cytotoxic T cells (TC).
  • The action of T cells is called the cellular response.
3) Activation of B cells

3) Activation of B cells

  • T-cells activate B lymphocyte cells (a type of white blood cell).
  • B cells divide into plasma cells.
  • The action of the B cells is called the humoral response.
4) Production of antibodies

4) Production of antibodies

  • Plasma cells secrete antibodies.
  • Antibodies are proteins that bind specifically to antigens on the cell surface membrane of pathogens.
Jump to other topics
1

Unity & Diversity - Molecules

1.1

Water

1.1.1Water & Hydrogen Bonding1.1.2IB Multiple Choice - Water & Hydrogen Bonding1.1.3Extended Response - Water
1.2

DNA Structure & Replication

1.2.1DNA1.2.2RNA1.2.3DNA Replication1.2.4DNA Replication - Summary1.2.5IB Multiple Choice - DNA Replication
1.3

Transcription & Gene Expression

1.3.1Introduction to Transcription & Protein Synthesis1.3.2Types of RNA1.3.3Transcription1.3.4RNA Processing in Eukaryotes1.3.5IB Multiple Choice - Transcription
1.4

Translation

1.4.1Translation1.4.2Retroviruses1.4.3Scientific Practices: Coronavirus1.4.4IB Multiple Choice - Translation
2

Unity & Diversity - Cells

2.1

The Origin of Cells

2.1.1Origins - Endosymbiosis
2.2

Introduction to Cells

2.2.1Introduction to Cells2.2.2Cell Size & Surface Area2.2.3Surface Area to Volume Ratio2.2.4Eukaryotic vs Prokaryotic Cells2.2.5Stem Cells2.2.6Stem Cells in Disease
2.3

Ultrastructure of Cells

2.3.1Golgi, Lysosomes & Ribosomes2.3.2Cell Walls & Vacuole2.3.3Prokaryotes2.3.4Binary Fission
2.4

Cell Division

2.4.1The Cell Cycle2.4.2Mitosis2.4.3Regulation of the Cell Cycle2.4.4End of Topic Quiz - The Cell Cycle2.4.5IB Multiple Choice - The Cell Cycle2.4.6Extended Response - Mitosis
2.5

Structure of DNA & RNA

2.5.1DNA & RNA
2.6

DNA Replication, Transcription & Translation

2.6.1Protein Synthesis2.6.2Transcription & Translation2.6.3End of Topic Test - DNA, Genes & Protein Synthesis2.6.4Exam-Style Question - Protein Synthesis2.6.5End of Topic Test - Coronavirus Translation2.6.6IB Multiple Choice - Transcription2.6.7IB Multiple Choice - Translation
2.7

Cell Respiration

2.7.1Overview of Respiration2.7.2Anaerobic Respiration2.7.3End of Topic Test - Anaerobic Respiration2.7.4Respiration Experiments2.7.5End of Topic Test - Respiration2.7.6IB Multiple Choice - Respiration
2.8

Photosynthesis

2.8.1Overview of Photosynthesis
2.9

Viruses

2.9.1Viruses
3

Unity & Diversity - Organisms

3.1

Diversity of Organisms

3.1.1Chromosomal Theory of Inheritance3.1.2Chromosomal Basis of Inherited Disorders3.1.3IB Multiple Choice - Chromosomal Inheritance
3.2

Evidence for Evolution

3.2.1Evidence for Evolution - Fossils & DNA3.2.2Evidence for Evolution - Anatomy & Geography3.2.3IB Multiple Choice - Evidence for Evolution3.2.4Extended Response - DNA & Evolution
3.3

Natural Selection

3.3.1Introduction3.3.2Evolutionary Fitness3.3.3Natural Selection & Variation3.3.4End of Topic Quiz - Natural Selection3.3.5IB Multiple Choice - Natural Selection3.3.6Speciation
4

Unity & Diversity - Ecosystems

4.1

Classification

4.1.1Introduction to Biodiversity4.1.2Keystone Species4.1.3Courtship & Ancestry4.1.4Classification
4.2

Cladistics

4.2.1Evolutionary Relationships4.2.2IB Multiple Choice - Species & Taxonomy
4.3

Evolution & Speciation

4.3.1Evidence for Evolution - Fossils & DNA4.3.2Evidence for Evolution - Anatomy & Geography4.3.3IB Multiple Choice - Evidence for Evolution4.3.4Extended Response - DNA & Evolution4.3.5Populations4.3.6Mutations, Genetic Drift, & Gene Flow4.3.7Speciation4.3.8Rate of Speciation4.3.9Allopatric & Sympatric Speciation
4.4

Conservation of Biodiversity

4.4.1Coming Soon!
5

Form & Function - Molecules

5.1

Carbohydrates & Lipids

5.1.1Monosaccharides5.1.2Disaccharides & Polysaccharides5.1.3Triglycerides & Phospholipids5.1.4Cellulose5.1.5Starch & Glycogen
5.2

Proteins

5.2.1Structure & Functions of Proteins
6

Form & Function - Cells

6.1

Membranes & Membrane Transport

6.1.1Passive Movement Across Membranes6.1.2Active Movement Across Membranes6.1.3Endocytosis & Exocystosis6.1.4Cell Membrane Structure & Permeability
6.2

Organelles & Compartmentalization

6.2.1Eukaryotic Cells & Organelles6.2.2Subcellular Components & Organelles
6.3

Cell Specialization

6.3.1Cell Specialization
7

Form & Function - Organisms

7.1

Gas Exchange

7.1.1Lung Structure & Alveoli7.1.2Ventilation7.1.3Lung Disease7.1.4Lung Disease Data
7.2

Transport

7.2.1The Circulatory System7.2.2The Heart7.2.3Blood Vessels7.2.4Cardiovascular Disease7.2.5Xylem Structure7.2.6Cohesion-Tension Theory7.2.7Investigating Transpiration Rate7.2.8Phloem Structure7.2.9Translocation
7.3

Muscle & Motility

7.3.1Skeletal Muscle7.3.2Sliding Filament Theory7.3.3Contraction
8

Form & Function - Ecosystems

8.1

Species, Communities & Ecosytems

8.1.1Population Dynamics8.1.2Communities & Measuring Diversity8.1.3Relationships Between Populations8.1.4Overview of Ecosystems8.1.5Nutrient Cycles8.1.6Fertilisers8.1.7Eutrophication8.1.8Chi-Squared Test
8.2

Energy Flow

8.2.1Energy8.2.2Energy Flow8.2.3Biomass & Food Chains8.2.4Heterotrophs & Autotrophs
8.3

Carbon Cycle

8.3.1Carbon Cycle
8.4

Climate Change

8.4.1Carbon Dioxide8.4.2The Greenhouse Effect8.4.3Global Warming8.4.4Maintaining Biodiversity
9

Interaction & Interdependence - Molecules

9.1

Enzymes

9.1.1Enzymes9.1.2Factors Affecting Enzyme Activity9.1.3Enzyme-Controlled Reactions9.1.4End of Topic Test - Enzymes
9.2

Metabolism

9.2.1Molecules to Metabolism
9.3

Cell Respiration

9.3.1Glycolysis9.3.2Aerobic Respiration
9.4

Photosynthesis

9.4.1Light-Dependent Reaction9.4.2Light-Independent Reaction9.4.3End of Topic Test - Photosynthesis Reactions9.4.4Limiting Factors9.4.5Photosynthesis Experiments9.4.6End of Topic Test - Photosynthesis9.4.7End of Topic Test - Photosynthesis
10

Interaction & Interdependence - Cells

10.1

Chemical Signalling

10.1.1Coming Soon!
10.2

Neural Signalling

10.2.1Medical Application10.2.2Speed of Transmission10.2.3Synapses10.2.4End of Topic Test - Nervous Comm&Coord10.2.5Neuron Structure10.2.6Types of Synapse10.2.7End of Topic Test - Neurones & Action Potentials10.2.8Transmission of an Impulse10.2.9End of Topic Test - Synapses
10.3

Adaptation to Environment

10.3.1Coming Soon!
10.4

Ecological Niches

10.4.1Coming Soon!
11

Interaction & Interdependence - Organisms

11.1

Integration of Body Systems

11.1.1Plant Tropisms
11.2

Defence Against Disease

11.2.1Immune System11.2.2The Immune Response11.2.3Antibodies11.2.4Primary & Secondary Response11.2.5Vaccines11.2.6HIV11.2.7End of Topic Test - Immune System
12

Interaction & Interdependence - Ecosystems

12.1

Populations & Communities

12.1.1Coming Soon!
12.2

Transfers of Energy & Matter

12.2.1Coming Soon!
13

Continuity & Change - Molecules

13.1

DNA Replication

13.1.1DNA Replication
13.2

Protein Synthesis

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13.3

Mutation & Gene Editing

13.3.1Genes13.3.2Mutations13.3.3DNA Technology13.3.4PCR & Gel Electrophoresis13.3.5Genetic Modification13.3.6Cloning
14

Continuity & Change - Cells

14.1

Gene Expression

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14.2

Water Potential

14.2.1Controlling Blood Water Potential
15

Continuity & Change - Organisms

15.1

Inheritance

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15.2

Homeostasis

15.2.1Overview of Homeostasis15.2.2Blood Glucose Concentration15.2.3Controlling Blood Glucose Concentration15.2.4End of Topic Test - Blood Glucose15.2.5Type I & Type II Diabetes15.2.6Human Reproductive Systems15.2.7Hormonal Control of the Menstrual Cycle15.2.8Kidneys & Osmoregulation
16

Continuity & Change - Ecosystems

16.1

Natural Selection

16.1.1Natural Selection
16.2

Stability & Change

16.2.1Coming Soon!
16.3

Climate Change

16.3.1Carbon Dioxide16.3.2The Greenhouse Effect16.3.3Global Warming16.3.4Maintaining Biodiversity

Practice questions on Immune System

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    Which of these is least likely to induce an immune response?Multiple choice
  2. 2
    Which of the following statements about the immune response are true?True / false
  3. 3
    How does the immune system respond to antigens?Fill in the list
  4. 4
    Which of the following statements about antigens are true?True / false
  5. 5
    Where are the complementary receptors to antigens located in immune cells?Multiple choice
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Plant Tropisms

The Immune Response