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49 Cards in this Set

  • Front
  • Back
How does the immune response start?
Foreign antigens on the surface of a pathogen trigger an immune response.
How do phagocytes engulf pathogens?

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.

What cells do phagocytes activate?

T-cells; they have receptor proteins bind to complementary antigens presented by phagocytes.
What are helper T-cells?
Cells that release chemical signals; activate and stimulate phagocytes as well as B-cells.

What are cytotoxic T-cells?

T-cells which kill abnormal and foreign cells.
What type of cells activate B-cells?
What are B-cells?
Type of white blood cell covered in antibodies which bind to complementary antigens to form antigen-antibody complex.

When the antibody on the surface a B-cell meets complementary antigen, what type of cell does the B-cell divide into?
They divide into plasma cells by mitosis.
What are plasma cells?
They are clones of B-cells which secrete lots of antibodies specific to antigen; 'monoclonal antibodies'.

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

Memory cells; remember specific antibody needed to bind to antigen.
What two types of response can the immune response be split into?
Cellular and Humoral response.

What does the cellular response involve?

T-cells and other immune system cells that T-cells interact with - eg. phagocytes.
What does the humoral response involve?
B-cells, clonal selection and production of monoclonal antibodies.
What is the primary response?
When an antigen enters the body for the first time and activates the immune response.
Why is the primary response slow?
No B-cells that divide by mitosis into plasma cells to produce antibody needed.
What happens as a result of the immune response being slow?
The infected person will show symptoms of the disease.
What is the secondary response?
If same pathogen enters body; immune system produces quicker, stronger immune response.
What happens faster in a secondary immune response?
Clonal selection; memory B-cells activated and divide into plasma cells which produce antibody needed.

What is often the case with the secondary immune response?

Immune system destroys pathogen before infected person shows symptoms.

Who can vaccines protect?

Individuals and populations against disease.

What do vaccines contain?

Foreign antigens that stimulate the production of memory cells against pathogen without causing symptoms.
What might the antigens in the vaccine be?

Free or attached to dead or attenuated (weakened) pathogen.
What is herd immunity?
Vaccinated people reduce occurrence of disease so those not vaccinated less likely to catch it.
What is the disadvantage of taking vaccines orally?
Vaccine could be broken down by enzymes in gut or molecules too large to be absorbed.

Why might booster vaccines be given later on?

To make sure memory cells are produced.
What is antigenic variation?
Pathogens change surface antigens meaning memory cells produced from first infection wont recognise different antigens.
Why do you get ill or show symptoms again?
The primary response is slow; no memory cells to recognise different antigens.
Antigenic variation means it is difficult to produce what?
Vaccines against diseases like HIV and influenza.
What two types of immunity are there?
Active and passive immunity.
What is active immunity?
The immune system makes own antibodies after being stimulated by antigen.

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

Natural - immune after catching disease.

Artificial - vaccination containing harmless dose of antigen.

What is passive immunity?
Immunity as a result from being given antibodies made by different organism.

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

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

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

Compare active and passive immunity?

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.

What are monoclonal antibodies?
Antibodies produced from single group of genetically identical B-cells (plasma cells).

What makes antibodies very specific?
The unique tertiary structure that is complementary to one particular antigen.
What context can monoclonal antibodies be used in?

Targeting drugs to particular cell type; cancer cells.

Targeting a particular substance for medical diagnosis; pregnancy testing.

Using ELISA as a HIV Test.

What is HIV?
A virus affecting immune system eventually leading to AIDS.
What type of cells does HIV infect and eventually kill?
Helper T-cells; they act as host cells.

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

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

When do people infected with HIV develop AIDS?

When helper T-cell numbers reach a critically low level.
What is the structure of HIV?

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.

Outline the process by which HIV replicates?

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.

What do the initial symptoms of AIDS include?

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

As AIDS progresses what symptoms might start to develop?
More serious infections including chronic diarrhoea, severe bacterial infections and tuberculosis.
During the late stages of AIDS patients have a very low number of immune system cells; what infections could this cause?

Toxoplasmosis of the brain and candidiasis of the respiratory system.
How do antibiotics kill bacteria?
Antibiotics interfere with bacterial metabolic reactions targeting enzymes and ribosomes.

Why don't antibiotics kill viruses?

Bacterial enzymes/ribosomes different to human; viruses use human enzymes and ribosomes to replicate; antibiotics cant inhibit them.
What do most anti-viral drugs target?
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.