The Immune System

Front 1

How does the immune response start?

Back 1

Foreign antigens on the surface of a pathogen trigger an immune response.

Front 2

How do phagocytes engulf pathogens?

Back 2

Phagocyte recognises the foreign antigens on a pathogen.

The cytoplasm of phagocytes moves around pathogen containing it within phagocytic vacuole.

A lysosome fuses with vacuole; lysozymes digest the pathogen.

Phagocyte presents pathogens antigens to activate other immune system cells.

Front 3

What cells do phagocytes activate?

Back 3

T-cells; they have receptor proteins bind to complementary antigens presented by phagocytes.

Front 4

What are helper T-cells?

Back 4

Cells that release chemical signals; activate and stimulate phagocytes as well as B-cells.

Front 5

What are cytotoxic T-cells?

Back 5

T-cells which kill abnormal and foreign cells.

Front 6

What type of cells activate B-cells?

Back 6

T-cells.

Front 7

What are B-cells?

Back 7

Type of white blood cell covered in antibodies which bind to complementary antigens to form antigen-antibody complex.

Front 8

When the antibody on the surface a B-cell meets complementary antigen, what type of cell does the B-cell divide into?

Back 8

They divide into plasma cells by mitosis.

Front 9

What are plasma cells?

Back 9

They are clones of B-cells which secrete lots of antibodies specific to antigen; 'monoclonal antibodies'.

Front 10

As well as plasma cells, what type of cell does a B-cell divide into?

Back 10

Memory cells; remember specific antibody needed to bind to antigen.

Front 11

What two types of response can the immune response be split into?

Back 11

Cellular and Humoral response.

Front 12

What does the cellular response involve?

Back 12

T-cells and other immune system cells that T-cells interact with - eg. phagocytes.

Front 13

What does the humoral response involve?

Back 13

B-cells, clonal selection and production of monoclonal antibodies.

Front 14

What is the primary response?

Back 14

When an antigen enters the body for the first time and activates the immune response.

Front 15

Why is the primary response slow?

Back 15

No B-cells that divide by mitosis into plasma cells to produce antibody needed.

Front 16

What happens as a result of the immune response being slow?

Back 16

The infected person will show symptoms of the disease.

Front 17

What is the secondary response?

Back 17

If same pathogen enters body; immune system produces quicker, stronger immune response.

Front 18

What happens faster in a secondary immune response?

Back 18

Clonal selection; memory B-cells activated and divide into plasma cells which produce antibody needed.

Front 19

What is often the case with the secondary immune response?

Back 19

Immune system destroys pathogen before infected person shows symptoms.

Front 20

Who can vaccines protect?

Back 20

Individuals and populations against disease.

Front 21

What do vaccines contain?

Back 21

Foreign antigens that stimulate the production of memory cells against pathogen without causing symptoms.

Front 22

What might the antigens in the vaccine be?

Back 22

Free or attached to dead or attenuated (weakened) pathogen.

Front 23

What is herd immunity?

Back 23

Vaccinated people reduce occurrence of disease so those not vaccinated less likely to catch it.

Front 24

What is the disadvantage of taking vaccines orally?

Back 24

Vaccine could be broken down by enzymes in gut or molecules too large to be absorbed.

Front 25

Why might booster vaccines be given later on?

Back 25

To make sure memory cells are produced.

Front 26

What is antigenic variation?

Back 26

Pathogens change surface antigens meaning memory cells produced from first infection wont recognise different antigens.

Front 27

Why do you get ill or show symptoms again?

Back 27

The primary response is slow; no memory cells to recognise different antigens.

Front 28

Antigenic variation means it is difficult to produce what?

Back 28

Vaccines against diseases like HIV and influenza.

Front 29

What two types of immunity are there?

Back 29

Active and passive immunity.

Front 30

What is active immunity?

Back 30

The immune system makes own antibodies after being stimulated by antigen.

Front 31

Give an example of active immunity that is natural and artificial?

Back 31

Natural - immune after catching disease.

Artificial - vaccination containing harmless dose of antigen.

Front 32

What is passive immunity?

Back 32

Immunity as a result from being given antibodies made by different organism.

Front 33

Give an example of passive immunity that is natural and artificial?

Back 33

Natural - baby becomes immune due to antibodies received via placenta/breast milk.

Artificial - immune after being injected with antibodies from someone else.

Front 34

Compare active and passive immunity?

Back 34

Active requires exposure to antigen; passive does not.

Active takes while for protection to develop; protection is immediate.

Active produces memory cells; passive does not.

Active is long term as antibody produces after activation of memory cells; protection is short term as antibodies broken down.

Front 35

What are monoclonal antibodies?

Back 35

Antibodies produced from single group of genetically identical B-cells (plasma cells).

Front 36

What makes antibodies very specific?

Back 36

The unique tertiary structure that is complementary to one particular antigen.

Front 37

What context can monoclonal antibodies be used in?

Back 37

Targeting drugs to particular cell type; cancer cells.

Targeting a particular substance for medical diagnosis; pregnancy testing.

Using ELISA as a HIV Test.

Front 38

What is HIV?

Back 38

A virus affecting immune system eventually leading to AIDS.

Front 39

What type of cells does HIV infect and eventually kill?

Back 39

Helper T-cells; they act as host cells.

Front 40

Why can this have a huge impact on the immune system to respond effectively?

Back 40

Helper T-cells send chemical signals to activate phagocyte, Cytotoxic T-cells and B-cells.

Front 41

When do people infected with HIV develop AIDS?

Back 41

When helper T-cell numbers reach a critically low level.

Front 42

What is the structure of HIV?

Back 42

Core; contains genetic material (RNA) and some proteins (reverse transcriptase enzyme).

Capsid; outer coating of protein.

Envelope; stolen cell membrane of host cell.

Attachment proteins; enables HIV attach to host helper T-cell.

Front 43

Outline the process by which HIV replicates?

Back 43

Attachment protein attaches to receptor molecule of host helper T-cell.

Capsid released into cell; uncoats and releases RNA into cell cytoplasm.

Reverse transcriptase makes complementary strand of DNA from viral RNA template.

Double stranded DNA made and inserted into human DNA.

Host cell enzymes used to make viral proteins from viral DNA.

Viral proteins assembled into new viruses.

Front 44

What do the initial symptoms of AIDS include?

Back 44

Minor infections of mucous membranes (eg. inside the nose, ears and genitals) and recurring respiratory infections.

Front 45

As AIDS progresses what symptoms might start to develop?

Back 45

More serious infections including chronic diarrhoea, severe bacterial infections and tuberculosis.

Front 46

During the late stages of AIDS patients have a very low number of immune system cells; what infections could this cause?

Back 46

Toxoplasmosis of the brain and candidiasis of the respiratory system.

Front 47

How do antibiotics kill bacteria?

Back 47

Antibiotics interfere with bacterial metabolic reactions targeting enzymes and ribosomes.

Front 48

Why don't antibiotics kill viruses?

Back 48

Bacterial enzymes/ribosomes different to human; viruses use human enzymes and ribosomes to replicate; antibiotics cant inhibit them.

Front 49

What do most anti-viral drugs target?

Back 49

Virus-specific enzymes; eg. HIV uses reverse transcriptase to replicate - humans don't use this so drugs can be designed to inhibit without affecting host cell.