Cell Recognition and the Immune System- The Immune System Flashcards

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1
Q

What are antigens?

A

Molecules (usually proteins) that trigger an immune response when detected by the body

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2
Q

Where are antigens found?

A

Usually on surface of cells

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3
Q

How are antigens used by the immune system?

A

To identify pathogens, abnormal body cells, toxins and non-self cells

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4
Q

What are the four main stages in the immune response?

A
  1. Phagocytes engulf pathogens
  2. Phagocytes activate T cells
  3. T cells activate B cells which divide into plasma cells
  4. Plasma cells make more antibodies to a specific antigen
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5
Q

How do phagocytes engulf pathogens (phagocytosis)?

A
  1. Phagocyte recognises foreign antigens on pathogen
  2. Cytoplasm of phagocyte moves round pathogen (engulfing it)
  3. Pathogen now contained in a phagosome
  4. Lysosome releases lysozymes which break down pathogen
  5. Phagocyte presents pathogen’s antigens
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6
Q

What is a phagocyte?

A

A type of white blood cell that carries out phagocytosis

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7
Q

Where are phagocytes found?

A

In blood and in tissues

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8
Q

What is a T cell?

A

A type of white blood cell

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9
Q

How are T cells activated?

A

The T cell has receptor proteins on its surface that bind to complementary antigens presented to it by the phagocytes

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10
Q

How can T cells respond?

A
TH cells (helper T cells) release chemical signals that activates and stimulates phagocytes and cytotoxic T cells (TC cells) which kill abnormal and foreign cells
They can also stimulate B cells
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11
Q

What are B cells?

A

A type of white blood cell that secretes antibodies

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12
Q

What does it mean that antibodies are specific?

A

Each B cell has a different shaped antibody so different ones bind to different shaped antigens

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13
Q

What happens when antibodies bind to antigens?

A

An antigen-antibody complex is formed and B cells are activated (clonal selection) which divides into plasma cells

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14
Q

What do plasma cells do?

A

They secrete lots of antibodies specific to the antigen called monoclonal antibodies that bind to the antigen on the pathogens surface to form antigen-antibody complex

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15
Q

What is an antibody?

A

Proteins made up of chains of amino acids

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16
Q

What does the specificity of an antibody depend on?

A

Its variable regions which form antigen binding sites

17
Q

What is agglutination?

A

Pathogens become clumped together as an antibody has two binding sites so can bind to two pathogens at the same time

18
Q

What is involved in cell-mediated immunity?

A

T cells and other immune system cells they interact with

19
Q

What is involved in humoral immunity?

A

B cells, clonal selection and the production of monoclonal antibodies

20
Q

What is the primary immune response?

A

When an antigens enters the body for the first time and activates the immune system

21
Q

What is the speed of the primary immune response?

A

Slow because there aren’t many B cells to make the antibody that is needed

22
Q

What happens in the primary immune response?

A

Over time, enough antibodies are produced to overcome the pathogen and the individual will show symptoms of the disease

23
Q

What will happen after being exposed to a pathogen?

A

Memory cells are produced that remain in the body for a long time and they remember the specific antigen and will recognise it when the individual is infected a second time

24
Q

What is the secondary immune response?

A

When the pathogen enters the body a second time, the memory cells recognise the antigen and produce more antibodies quicker

25
Q

What is the speed of the secondary immune response?

A

Quick and strong

26
Q

What happens in the secondary immune response?

A

Clonal selection happens faster, memory B cells are activated and divide into plasma cells that produce the correct antibody to fit the antigen, memory T cells are activated and divide into the correct type of T cells to kill the cell

27
Q

Does the individual show symptoms with the secondary immune response?

A

The secondary immune response often gets rid of the pathogen before showing any symptoms