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Biology A LEVEL > Vaccines and Immunity > Flashcards

Vaccines and Immunity Flashcards

1
Q

What is the role of T lymphocytes (T cells)?

A
  • involved in the specific immune response
    (second line of defense after a pathogen enters the bloodstream)
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2
Q

Where are T cells made and where do they mature?

A
  • bone marrow
  • mature in the thymus.
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3
Q

What is the cell-mediated response?

A

the response involving T cells reacting specifically to antigens presented on antigen-presenting cells

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4
Q

What are antigen-presenting cells (APCs)?

A

Cells that display non-self antigens on their surface

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5
Q

Examples of APC’s?

A
  1. Infected cells presenting viral antigens.
  2. Macrophages after phagocytosis.
  3. Cells of transplanted organs.
  4. Abnormal cells like cancer cells.
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6
Q

Why is it called the cell-mediated response?

A

T cells only respond to antigens on the surface of cells, not free-floating antigens in bodily fluids

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7
Q

What happens when a T helper cell binds to an antigen-presenting cell?

A

The receptor on the T helper cell binds to the antigen on the APC, activating the T helper cell

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8
Q

What occurs after T helper cells are activated?

A

They divide by mitosis to form clones of T helper cells

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9
Q

What happens to the cloned T helper cells?

A

They can:

  1. Stimulate B cells (humoral response).
  2. Stimulate macrophages for more phagocytosis.
  3. Become memory T cells.
  4. Become cytotoxic (killer) T cells.
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10
Q

What do cytotoxic (killer) T cells do?

A

destroy infected or abnormal cells by releasing perforin a protein that creates pores in the cell membrane, causing cell death

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11
Q

How does perforin work?

A
  • It embeds into the cell membrane of an infected cell, creating a pore.
  • Substances enter and exit the cell, leading to its death.
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12
Q

Why are cytotoxic T cells important in viral infections?

A

They kill virus-infected cells to prevent the virus from replicating and spreading.

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13
Q

What causes a sore throat during a viral infection?

A

Cytotoxic T cells destroy infected throat cells, preventing viral replication but causing soreness

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14
Q

What are the key types of cells involved in the cell-mediated response?

A
  1. Helper T cells: Stimulate other immune cells.
  2. Memory T cells: Retain information about antigens.
  3. Cytotoxic T cells: Destroy infected or abnormal cells.
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15
Q

What are the steps in the cell-mediated response.

A
  1. Antigen from pathogen is displayed on the cell surface of body cells
  2. t cells with correct specific receptor bind with antigen and are activated
  3. Helper T cells divide by mitosis
  4. Helper T cells stimulate B cells, macrophages, or differentiate into memory/cytotoxic T cells.
  5. Cytotoxic T cells release perforin to destroy infected cells.
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16
Q

What is phagocytosis?

A

nonspecific immune response where phagocytes (e.g., macrophages) engulf and destroy pathogens or non-self substances

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17
Q

What are phagocytes?

A
  • also known as macrophages
  • white blood cells that carry out phagocytosis
  • found in the blood and tissues
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18
Q

What does “nonspecific response” mean in phagocytosis?

A

phagocytes respond the same way to any non-self substance, regardless of the specific antigen

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19
Q

What is the role of white blood cells in the immune response?

A

provides nonspecific responses (e.g phagocytosis by phagocytes) and specific responses (e.g., lymphocytes).

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20
Q

What attracts phagocytes to pathogens or abnormal cells?

A

Chemicals, toxins, or debris released by pathogens or abnormal cells attract phagocytes

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21
Q

How do phagocytes bind to pathogens?

A

Receptors on the phagocyte’s surface bind to antigens or chemicals on the pathogen’s surface.

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22
Q

What happens after a phagocyte binds to a pathogen?

A

The phagocyte changes shape to engulf the pathogen, forming a vesicle around it called a phagosome

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23
Q

What is a phagosome?

A

the vesicle within a phagocyte that contains the engulfed pathogen

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24
Q

What is the role of lysosomes in phagocytosis?

A

fuse with the phagosome, releasing lysozymes (enzymes) into it to break down the pathogen.

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25
Q

What is lysozyme, and what does it do?

A

an enzyme in lysosomes that hydrolyzes and destroys pathogens inside the phagosome

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26
Q

What happens to the broken-down pathogen in the phagosome?

A

The soluble products are absorbed and recycled by the phagocyte.

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27
Q

What is an antigen-presenting cell (APC)?

A

After phagocytosis, the phagocyte displays the pathogen’s antigen on its surface, becoming an antigen-presenting cell (APC)

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28
Q

What is the significance of antigen-presenting cells (APCs)?

A

presents antigens to T cells, triggering a specific immune response

29
Q

Summary of the process of phagocytosis

A
  1. Phagocytes detect and move towards pathogen chemicals.
  2. They bind to the pathogen and engulf it, forming a phagosome.
  3. Lysosomes fuse with the phagosome, releasing lysozymes to hydrolyze the pathogen.
  4. Soluble products are absorbed, and the phagocyte becomes an APC.
30
Q

Why is phagocytosis considered nonspecific?

A

It occurs the same way regardless of the type of foreign particle, whether it’s an abnormal cell, pathogen, or transplant cell.

31
Q

What is the humoral response?

A

a specific immune response involving B cells and antibodies

32
Q

Where are B cells made and matured?

A

bone marrow

33
Q

What do B cells do?

A

produce antibodies and participate in specific immune responses by responding to particular antigens

34
Q

How do B cells recognize antigens?

A

Each B cell has specific antibodies on its surface that are complementary to a particular antigen

35
Q

What happens when a B cell binds to its complementary antigen?

A
  • The B cell takes in the antigen by endocytosis
  • presents it on its surface and
  • becomes activated by a helper T cell.
36
Q

What is clonal selection?

A

the process where an activated B cell undergoes mitosis to produce identical clones which differentiate into plasma cells and memory B cells

37
Q

What do plasma cells do?

A

produce large quantities of antibodies to help destroy pathogens

38
Q

What do memory B cells do?

A
  • remain in the body for decades
  • rapidly divide into plasma cells if they encounter the same antigen again
39
Q

What is the difference between the primary and secondary immune response?

A
  • Primary Response: Slower and produces fewer antibodies when encountering a pathogen for the first time
  • Secondary Response: Faster and produces more antibodies due to memory B cells
40
Q

Why don’t we get symptoms during the secondary immune response?

A

Memory B cells enable rapid production of antibodies, destroying the pathogen before symptoms develop

41
Q

What is the structure of an antibody?

A
  • quaternary proteins
  • made of four polypeptide chains (two heavy, two light)
  • variable region binds to specific antigens.
  • constant region remains the same in all antibodies
42
Q

What is agglutination?

A
  • the clumping together of pathogens when antibodies bind to multiple antigens
  • makes it easier for phagocytes to engulf them.
43
Q

How do antibodies help destroy pathogens?

A
  1. Antibodies bind to antigens, forming antigen-antibody complexes.
  2. Agglutination occurs, making pathogens easier for phagocytes to locate and engulf.
44
Q

What are the two main types of cells produced by clonal selection?

A
  • Plasma Cells: Produce antibodies.
  • Memory B Cells: Provide long-term immunity by rapidly producing plasma cells if re-exposed to the antigen.
45
Q

Process of the humoral response

A

B cells bind to antigens and are activated by helper T cells.
Activated B cells undergo clonal selection to produce plasma cells and memory cells.
Plasma cells release antibodies, and memory cells provide long-term immunity.
Antibodies bind to antigens, forming complexes and leading to agglutination, which aids phagocytes in destroying pathogens.

46
Q

What is active immunity?

A

occurs when the body is exposed to a pathogen, producing memory cells and antibodies for long-term protection

47
Q

What allows the immune system to distinguish between self and non-self cells?

A

Molecules on the cell surface membrane, called antigens, act as unique markers that lymphocytes recognize

48
Q

What are antigens typically made of?

A

Proteins with distinct 3D shapes.

49
Q

What types of non-self cells can lymphocytes recognize?

A
  • Pathogens (e.g., bacteria, fungi, viruses).
  • Cells from organ transplants.
  • Abnormal body cells (e.g., cancer cells).
  • toxins (e.g., cholera toxins).
50
Q

How do lymphocytes ensure they don’t attack self-cells during fetal development?

A
  • Lymphocytes complementary to self-antigens are destroyed or suppressed.
    -This ensures only lymphocytes targeting non-self antigens remain active.
51
Q

What happens if lymphocytes mistakenly attack self-cells?

A

can lead to autoimmune diseases, where the immune system harms the body’s own cells

52
Q

How many types of lymphocytes does the human body have?

A

Approximately 10 million types, each recognizing one unique antigen

53
Q

Where does lymphocyte selection continue after birth?

A

bone marrow

54
Q

What is antigen variability?

A

Frequent mutations in a pathogen’s DNA can change the shape of its antigens, making previous immunity or vaccines ineffective

55
Q

Why is a new flu vaccine needed each year?

A

influenza virus mutates frequently, changing the shape of its antigens so prior vaccines or immunity no longer work

56
Q

What are the key roles of antigens?

A
  • Act as markers to identify cells.
  • Trigger immune responses by lymphocytes.
57
Q

What happens to lymphocytes complementary to self-cells during development?

A

They are destroyed or suppressed to prevent them from attacking the body

58
Q

What are the consequences of antigen variability?

A
  • Loss of immunity from prior infections.
  • Ineffectiveness of previous vaccines.
59
Q

What is passive immunity?

A

when antibodies are introduced into the body rather than being created by the immune system.

60
Q

What are examples of passive immunity?

A
  • Antibodies passed through the placenta to a fetus.
  • Antibodies in breast milk for a baby.
  • Antibodies injected to neutralize toxins, such as snake venom.
61
Q

What are the characteristics of passive immunity?

A
  • Fast-acting
  • No memory cells are produced
  • Provides no long-term immunity
62
Q

What are the two types of active immunity?

A
  • Natural active immunity: Created after infection with a pathogen.
  • Artificial active immunity: Created by vaccination.
63
Q

What is a vaccine?

A

contains a weakened or dead form of a pathogen that stimulates the immune system to produce antibodies and memory cells

64
Q

How do vaccines work?

A

Vaccines expose lymphocytes to antigens, triggering clonal selection, clonal expansion, and differentiation into plasma cells and memory B cells

65
Q

What is the role of memory B cells in immunity?

A

they remain in the blood for decades, enabling rapid production of antibodies upon re-exposure to the pathogen

66
Q

What is herd immunity?

A

When enough of the population is vaccinated, it prevents the spread of a pathogen, protecting those who cannot be vaccinated

67
Q

Why is herd immunity important?

A
  • protects vulnerable individuals
  • such as infants, the elderly
68
Q

What are the key differences between active and passive immunity?

A
  • Active immunity: Body produces its own antibodies; includes memory cells for long-term protection.
    -Passive immunity: Antibodies are introduced externally; no memory cells or long-term protection.
69
Q

What is immunity

A

The ability to resist infection

Biology A LEVEL (9 decks)

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