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(2) Cells > 2.5 Immunity > Flashcards

2.5 Immunity Flashcards

1
Q

Name 3 of the body’s defence mechanisms against pathogens.

A
  • non-specific responce: skin barrier, mucus, OR phagocytsosis
  • inflammation
  • specific immune response
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2
Q

What is an antigen?

A

A glycoprotein found on the cell-surface membrane that triggers an immune response and identifies a cell as self or non-self.

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3
Q

What is antigenic variability?

A

When the antigens on the surface of a pathogen change frequently due to genetic mutations.

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4
Q

Why is antigenic variability a problem?

A
  1. The surface receptors on lymphocytes and memory cells are complementary in shape to only one antigen.
  2. When the antigen on a pathogen changes shape the lymphocytes and memory cells can no longer bind
  3. As a result, there is no secondary immune response
  4. The host gets re-infected and suffers from the disease again
    - previous immunity is no longer effective as memory b cells will have memory of the old antigen shape, so NO LONGER COMPLEMENTARY
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5
Q

What are the two types of phagocytes?

A
  • neutrophils
  • macrophages
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6
Q

Describe the process of phagocytosis.

A
  1. The pathogens adheres to the phagocyte (Chemotaxis)
  2. The pathogen binds to the specific receptors on the surface of the phagocyte
    3.. The phagocyte engulfs the pathogen (Endocytosis)
  3. Lysosome fuses with the phagosome vesicle
  4. Lysosomes digest the phagocyte by secreting lysozymes
  5. Antigens are displayed on the cell surface membrane of APCs
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7
Q

Where do T-lymphocytes mature?

A

Thymus

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8
Q

Where do B-lymphocytes mature?

A

Bone Marrow

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9
Q

What are the two types of T-cell?

A
  • T-helper cells
  • T-cytotoxic cells
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10
Q

Describe the T-lymphocyte response.

A
  1. T-cells have a specific receptor site that binds to the antigens presented on the surface of the phagocyte
  2. This stimulated the t-cells to divide by mitosis
  3. The t-cells then differentiate into t-helper cells and t-cytotoxic cells
    T-helper cells: involved in the B-lymphocyte response
    T-cytotoxic cells: release cytotoxins that destroy the pathogens
    - cell mediated response
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11
Q

Describe the B-lymphocyte response.

A
  1. B-cells take in antigens by endocytosis and present them on their surface
  2. Then the t-helper cell binds to these antigens
  3. This stimulates the b-cells to divide by mitosis (clonal selection)
  4. This makes b-memory cells and plasma cells
    B-memory cells: stimulate a secondary immune response
    Plasma cells: produce soluble antibodies specific to the antigen
    - humoral response
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12
Q

What is an antibody?

A

A immunoglobulin specific to an antigen produced by plasma cells in the immune system in response to foreign substances.

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13
Q

Describe the structure of an antibody?

A
  • quaternary structure
  • two short chains, two long chains
  • each polypeptide chain has a constant and variable region
  • binding site on end of variable region
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14
Q

Describe how an antibody-antigen complex is formed.

A
  • antigen and antibody are complementary
  • specific binding site on antibody binds to antigen to form and antigen-antibody complex
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15
Q

What is agglutination?

A

Process in which pathogens get clumped together.

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16
Q

What is a vaccine.

A

small amounts of weakened/ dead pathogen intentionally put into the body to induce artificial active immunity, where antibodies are secreted by plasma cells.

17
Q

What are the two types of vaccine?

A
  • live attenuated
  • dead/inactivated
18
Q

What is herd immunity?

A

Herd immunity arises when a sufficiently large proportion of the population has been vaccinated (and are therefore immune) which reduces the likelihood of the pathogen spreading within that population.

19
Q

What is active immunity?

A
  • acquired when antigens enter the body
  • triggers a specific immune response
  • naturally acquired through exposure to pathogens or artificially acquired through vaccines
  • produces memory cells for long-term immunity
20
Q

What is passive immunity?

A
  • acquired without an immune response
  • no antibodies produced
  • no memory cells
21
Q

How is HIV transmitted?

A
  • sexual intercourse
  • blood transfusions
  • mother to child (breast milk)
  • mother to child (placenta)
  • sharing needles
22
Q

Describe the structure of HIV.

A
  • two RNA strands
  • reverse transcriptase
  • capsid
  • attachment proteins
  • viral envelope (lipid bilayer and glycoproteins)
23
Q

How does HIV replicate?

A
  1. Attachment proteins attach to receptors on helper T cell/lymphocyte
  2. Nucleic acid/RNA enters cell
  3. Reverse transcriptase converts RNA to DNA
  4. Viral protein/capsid/enzymes produced
  5. Virus particles assembled and released from cell
24
Q

Describe how HIV replicates once inside helper T cell

A
  1. RNA converted into DNA using reverse transcriptase;
  2. DNA incorporated/inserted into helper T cell
  3. DNA transcribed into HIV mRNA
  4. HIV mRNA translated into new HIV/viral proteins for assembly into viral particles
25
Q

Why can’t antibiotics be used to treat HIV.

A

Antibiotics are ineffective against viruses as they are non-living.

26
Q

What are the symptoms of AIDS?

A
  • mild flu-like symptoms
  • weakened immune system (HIV destroys helper T-cells which means B-cells can’t be stimulated, therefore antibodies can not be made.)
27
Q

What are the treatments of HIV?

A
  • antiretroviral therapy
28
Q

What is a monoclonal antibody.

A

Antibodies with the same tertiary structure produced from identical plasma cells.

29
Q

What are the uses of monoclonal antibodies?

A
  • diagnosing HIV, tumours and other pathogens (medical diagnosis)
  • pregnancy tests
  • detecting blood clots
  • can be attached to therapeutic drugs
30
Q

What are some ethical issues associated with vaccines and mAbs?

A
  • use of animals (testing deemed to be unethical)
31
Q

Describe the role of antibodies in producing a positive result in an ELISA test

A
  1. First antibody is complementary in shape to antigen so binds
  2. Second antibody with enzyme attached is added
  3. Second antibody attaches to antigen (direct ELISA test)
    OR attaches to first antibody (indirect ELISA test)
  4. Substrate added and colour changes (+ve)

(2) Cells (5 decks)

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