Immunity AS Biology AQA

  • Created by: Alice
  • Created on: 20-05-14 11:51

How do vaccines protect people against disease?

Vaccines consist of dead or weakened pathogens which stimulate active immunity. 

The antigens on the pathogens are specific proteins which trigger an immune response. 

Memory cells and plasma cells are created through Humoral Immunity - B Cells are activated by T Helper Cells to divide by mitosis to create the Memory and Plasma Cells. 

On first exposure the plasma cells divide into antibodies which are specific to the antigen. The memory cells remain in the blood plasma. 

On second exposure, the response is faster and more antibodies are produced as the Memory Cells are already in the blood plasma, ready to divide into the plasma cells and antibodies.

This fights off the pathogens and ultimately kills them. Vaccination can allow herd immunity where the vulnerable population are targeted and the disease does not spread. 

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Features of a successful vaccination programme

1. Economically available

2. Few side effects

3. Means of storing, transporting, and producing

4. Means of administering 

5. Herd Immunity

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How does vaccination fail to eliminate a disease?

1. Defective immune systems

2. Ethical objections

3. Vaccination can be too late - disease develops before immunity levels do 

4. Pathogen can hide in other cells in the body

5. Too many strains to produce an effective vaccine against

6. Strains are constantly mutating so vaccination is not long-lasting or effective 

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1. Proteins - made up of four polypeptide chains 

2. Variable region is specific to each antibody which is complementary to an antigen

3. Moves like a hinge to fit around antigen 

4. Creates antigen-antibody complexes from the binding sites at end of light chains

5. Receptor binding site at bottom

Monoclonal antibodies

1. Single, isolated type of antibody. Cloned for mass production for several uses -

1. Immunoassay

2. Separating a chemical from a mixture

3. Cancer treatment

4. Transplant surgery

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T Cells

1. Phagocyte presents antigen on surface of T Cell

2. T-helper cell receptors fit exactly onto antigen, activate division by mitosis

3. T Cell clones created, which:

4. Develop into hole-making proteins to kill pathogens

5. Make B Cells

6. Make Memory Cells

7. Stimulate Phagocytosis

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B Cells

1. Pathogen's antigen taken up by B Cell, processed and presented on surface

2. T Helper Cell receptor fits exactly onto the antigen, activates T Cells to divide by Mitosis

3. Create Plasma and Memory Cells 

4. Plasma Cells divide into antibodies, Memory Cells divide into plasma cells to make more antibodies

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Problems controlling TB and Cholera by vaccination


1. Refugees in cramped conditions are unreachable by vaccination and spread the disease between them

2. Mobile populations migrate around and do not stay in one place

3. Increasing elderly population

4. Defective immune systems due to HIV so can be easily infected 


1. Intestinal disease - Immune System doesn't reach there

2. Mobile populations 

3. Antigens constantly changing so cannot develop a long lasting vaccination against it 

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1. Proteins - non self foreign entities which trigger an immune response 

2. Antigenic variability - some viruses like Influenza have over 100 strains - antigens constantly changing so the antibodies we produce aren't effective - have to rely on primary response for new strains that infect us which is a lot slower

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1. Pathogen attracted to phagocyte by chemoattractants

2. Pathogen engulfed by phagocyte, forms vesicle called phagosome

3. Lysosomes migrate in phagosome, release lytic enzymes which digest pathogen and debris is released in exocytosis. 

4. Causes inflammation from release of histamine.

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