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Biology > Cells: The immune system > Flashcards

Cells: The immune system Flashcards

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1
Q

What is an antigen

A

They are foreign chemical markers (usually proteins) on the surface of a cell membrane or viral particles that can generate an immune response

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2
Q

What do antigen allow the immune system to identify

A
  • Pathogens
  • Abnormal body cells (Cancerous or pathogen-infected cells)
  • Toxins (Poison)
  • Cells from other individuals of the same species (from blood/organ transplants of diff blood types)
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3
Q

What several defence mechanisms do our bodies have against pathogens

A

*Preventing entry:

  • Inflammation:
  • Recognising ‘foreign’ cells
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4
Q

State the difference between specific and non-specific immune response

A
  • Specific immune responses protects the body against specific pathogens as the responses are tailored to the particular pathogen

WHEREAS

  • Non-specific immune response is the same for all pathogens
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5
Q

Outline the first line of defences our body has

A
  • The skin - acts as a barrier preventing bacteria from getting in AND secretes enzymes (found in sweat) that can kill bacteria
  • The lungs - secretes mucus which traps pathogens and removes it through the ciliated epithelial cells
  • Stomach - secretes hydrochloric acid that kills pathogens
  • Eyes - secretes tears that contains enzymes that digest pathogens
  • Blood - contains white blood cells that eliminate pathogens
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6
Q

List how pathogens are spread

A
  • Food and water
  • Insect bite
  • Direct contact
  • Indirect contact
  • Airborne droplets
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7
Q

What are the main stages of the immune response

A
  • Phagocytosis
  • Cell mediated response (T-lymphocytes)
  • Humoral response (B- lymphocytes , antibody production)
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7
Q

Describe what occurs during phagocytosis

A
  • A phagocyte recognises the foreign antigen on a pathogen AND phagocyte the binds to the pathogen via receptors
  • THEN the cytoplasm of the phagocyte move around the pathogen - engulfing it via endocytosis WHICH forms a phagosome (a phagocytic vacuole)
  • AFTER the lysosomes fuse with the pathogen and the lysozymes break down the pathogen into soluble materials
  • THEN the phagocyte presents the pathogens antigens on its surface t o activate other immune system cells AND the phagocyte is acting as an antigen-presenting cell
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8
Q

What is endocytosis

A

It is a cellular process in which substances are brought into the cell

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9
Q

What are the two types of white blood cells

A
  • T-lymphocytes (T-cells)
  • B-lymphocytes (B-cells)
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10
Q

What response are T cells involved in

A

The cell mediated response

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11
Q

What response are B cells involved in

A

The humoral response

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12
Q

Describe what happens in the cell mediated response

A
  • T-cells have receptor proteins on its surface that minds to complementary antigens presented to it by phagocytes
  • THIS activates the T-cell and stimulates the differentiation of the T-cells AND/OR undergoes clonal expansion (mitosis)
  • T-cells differentiate into helper T-cells, cytotoxic T-cells and memory T-cells
  • Helper T-cells also activate B-cells allowing then to undergo clonal selection
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13
Q

State the function of helper T-cells and what they are

A
  • They are a type of immune cell
  • They release chemical signals that activate and stimulate phagocytes and cytotoxic T-cells
  • They also activate B-cells
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13
Q

State the function of cytotoxic T-cells and what they are

A

They are a type of immune cell which kill abnormal and foreign cells

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14
Q

What are antibodies

A

Proteins that have binding sites that are commentary to the antigens (to form antigen-antibody complexes) AND destroys the pathogen by releasing substances e.g perforin

15
Q

Describe what happens in the humoral response

A
  • B-cells (covered in antibodies) binds to an antigen complementary to the shape of the antibody on its surface (clonal selection)
  • The pathogen is endocytosed (engulfed) , and the antigen presented on the plasma membrane
  • Helper T-cells binds to the presented antigen (now on the surface of the B-cell) WHICH stimulates the B-cells to divide by mitosis (clonal expansion) and differentiate into plasma cells and memory B-cells
16
Q

What are plasma cells

A

A type of immune cell that makes large amounts of a specific antibody

17
Q

What are the antibodies that plasma cells secrete called

A

Monoclonal antibodies

18
Q

How many binding sites does an antibody have (and how is it relative to the amount of foreign antigens it can bind to)

A

Two - it can bind to two foreign antigens at the same time causing the pathogens to become clumped together

19
Q

What is agglutination

A

The clumping together of cells or particles caused by antibodies which assists phagocytosis

20
Q

Why is agglutination beneficial

A

It allows phagocytes to bind to the antibodies and phagocytose many pathogens at once - which leads to the destruction of pathogens which carry the antigen

21
Q

What region stays the same in antibodies

A

The constant regions

22
Q

What does the specificity of an antibody depend on

A

The variable region - which has a unique tertiary structure (due to the different amino acid sequencing

23
Q

What region of an antibody forms antigen binding sites

A

The variable region

24
Q

What is the primary immune response

A

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

25
Q

What is the secondary immune response

A

When the same pathogen enters the body again, producing a quicker and stronger immune response

26
Q

Why does the immune system produce a quicker, stronger response during the secondary immune response

A
  • Clonal selection happens faster
  • Memory B-cells are activated and divide into plasma cells that produce the right antibody to the antigen
  • Memory T-cells are activated and divide into the correct type of T-cells to kill the cell carrying the antigen
  • THIS OFTEN HAPPENS BEFORE ANY SYMPTOMS BEGIN TO SHOW
27
Q

What do T- and B-cells produce after being exposed to an antigen

A

Memory cells

28
Q

State the role of memory T-cells

A

Remember the specific antigen and remember it for the second time around

29
Q

State the role of memory B-cells

A

Record the specific antibodies needed to bind to the antigen

Biology (38 decks)

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