Immune response Flashcards

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1
Q

What is a pathogen and how do they cause disease?

A

An organism that causes disease AND an immune response by destroying cells and releasing toxins

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2
Q

What is an antigen?

A

A protein with a specific tertiary structure found on the the surface of cells (antigens not found in body are “non-self” or “foreign”) - cause an immune response

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3
Q

What are the defence systems in the body?

A
  • Non-specific (immediate) - physical barrier, phagocytosis
  • Specific (slower) - cellular/humoral response
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4
Q

What are the 3 first lines of defence?

A

HCl, mucus and skin

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5
Q

What is the anagram for phagocytosis?

A

PREP F E H A M

Phagocyte - white blood cell contains lysosomes
Recognises foreign antigens
Engulfs pathogen
Phagosome (pathogen inside a membrane)
Fuses with a lysosome
Enzymes - lysozymes released into phagosome
Hydrolyse molecules in pathogen
Antigen presenting cell - foreign antigens presented on the..
Membrane (cell surface)

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6
Q

What are the two types of T cell?

A
  1. Helper T cells stimulate phagocytes, B cells and cytotoxic T cells
  2. Cytotoxic T cells kill infected cells by making the membrane fully permeable so cell dies (can’t synthesise viruses)
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7
Q

What is clonal selection?

A

A specific T cell binds to presented antigen via its complementary receptor –> T cell activated and produces clones by mitosis to produce many T cells with complementary receptors to the antigen –> become either TH or TC cells

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8
Q

What is the anagram for the cellular response?

A

An Armadillo Starts To Crawl Can He Stop Before Passing (out)

Antigen presenting cell will
Activate a
Specific
T cell which will
Clone by mitosis, forming
Cytotoxic T cells which kill infected cells
Helper T cell
Stimulates
B cells
Phagocytes

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9
Q

What is a B cell?

A

A white blood cell responsible for producing antibodies - each produce a specific antibody

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10
Q

How are specific B cells activated?

A

Has protein receptors that are complementary to an antigen presented by a phagocyte or a receptor on an activated helper T cell - when these bind B cell is activated

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11
Q

What is the anagram for the humoral response?

A

Trevor Always Back Chats PAM

T helper cell
Activates
B cell (specific)
Clones by mitosis to form
Plasma cells which secrete
Antibodies
Memory cells formed

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12
Q

What is the secondary immune response?

A

More antibodies produced more quickly

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13
Q

What is the structure of an antibody?

A
  • Variable region (complementary to 1 antigen)
  • Constant region (same in every antibody)
  • Antigen-antibody complex
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14
Q

What are monoclonal antibodies?

A

Have the same tertiary structure and produced from the same plasma/B cell

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15
Q

How are monoclonal antibodies used in treating/diagnosing cancer?

A
  1. Monoclonal antibody complementary to cancer cell antigen binds to tumour markers on cancer cell
  2. Treatment - maintains high drug concentration at tumour site
  3. Diagnosis - tissue examined under microscope, fluorescent tag shows up for complementary antibody
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16
Q

What are ethical issues involved with the use of monoclonal antibodies?

A
  • Involves inducing tumours in mice
  • Mice are genetically engineered to produce human antibodies
  • Major side effects
17
Q

How does direct ELISA test for HIV?

A
  1. HIV antigen bound to bottom of well
  2. Add antibody + enzyme
  3. Wash to remove false positives
  4. Add substrate (when enzyme reacts with substrate = colour change)

Colour change = antigen/antibody testing for

18
Q

How does indirect ELISA test for HIV?

A
  1. HIV antigen bound to bottom of well
  2. Plasma sample added (might contain several different antibodies)
  3. Wash out well to remove unwanted antibodies which are unbound
  4. Secondary antibody added - antibody + enzyme that is complementary to HIV antigen
  5. Wash out to prevent false positives
  6. Substrate added - colour change = HIV is present
19
Q

What is immunity?

A

The ability of an organism to resist infection

20
Q

What are the 2 types of immunity?

A

Passive and active

21
Q

Compare the 2 types of immunity

A

Passive: Doesn’t require exposure to antigen, immediate protection, no memory cells produced, short term protection (antibodies hydrolysed) so needs to be redone

Active: Requires exposure to antigen, slower protection, memory cells produced, long term protection

22
Q

How does a vaccine stimulate an immune response?

A

Vaccines contain antigens –> phagocytosis –> T cell cellular response –> B cell humoral response –> memory cells = more antibodies more quickly when re-infected

23
Q

Why are vaccination programmes useful?

A

Herd immunity developed when vaccinations are carried out on large scales

24
Q

What are the ethical concerns with vaccination programmes?

A
  • Often involves animals
  • Side effects
  • Who should they be tested on?
25
Q

What is antigenic variability?

A

Some pathogens have antigens that can constantly change (strains)

26
Q

What is agglutination?

A

All pathogens become clumped together (attracts phagocytes)