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Immunology (BY1IM1) > Intro > Flashcards

Intro Flashcards

1
Q

What is Autoimmunity?

A

The immune system attacks the body

(relating to disease caused by antibodies or lymphocytes produced against substances naturally present in the body.)

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2
Q

Define Allergy

A

The immune system overreacts to something harmless

(A damaging immune response by the body to a substance, especially a particular food, pollen, fur, or dust, to which it has become hypersensitive)

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3
Q

What is cancer?

A

Tumours evade killing by the immune system which allows them to survive and proliferate

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4
Q

What is Immunosuppression?

A

Important components of the immune system are missing or destroyed

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5
Q

Define immunity

A

Immunity provides protection from infectious disease

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6
Q

How does the immune system protect the body from pathogens?

A
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7
Q

Immune system strategies: Physical barriers

A
  • First line of defence
  • Stop anything (especially pathogens) from getting in
  • Kill pathogens that do get in – gastric acid, gut microbiota
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8
Q

Give examples of immune systems first line of defence

A

Skin, mucus, and epithelia lining tubular organs (lungs, gut, genitourinary tract)

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9
Q

Immune system strategeies: Innate immune response

A
  • Second line of defence after physical barriers
  • interface between body cells and the extrenal environment
  • Innate means ‘existing at the time of birth’
  • Works very quickly but has no ‘memory’
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10
Q

Give examples of innate immune cells/ responses

A
  • Macrophages (rides in quickly, attack the invader, and delivers information to organize the defence) responsible for detecting, engulfing and destroying pathogens and apoptotic cells. Macrophages are produced through the differentiation of monocytes, which turn into macrophages when they leave the blood
  • dendritic cells (quietly lies in wait and surveys its environment. When something suspicious shows up, the DC collects information and shares it with T cells)
  • natural killer cells (they rapidly detect intruders and dispose of them with their armaments) specifically destroy viral infected cells. Uses the pore forming protein perforin in the cell membrane and the enzyme granzyme which initiates the apoptotic cascade and the viral infected cell dies (and the viral DNA is destroyed).
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11
Q

Are immune cells fixed?

A

Immune cells aren’t fixed; they can move around within your body

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12
Q

Which cells are the first to defend against attack?

A

Macrophages

Macro means BIG

Phage means EAT,

so the macrophages are big, hungry cells that devour bacteria in a process called “phagocytosis” (cell-eating)

They extend pseudopodia and extend to target and brings it inside the cell to be ‘eaten’

abbreviated as MΦ (M-phi)

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13
Q

What do macrophages eat?

A
  • Macrophages eat invaders (bacteria)
  • Macrophages eat rubbish (cell debris)
  • Macrophages eat dead cells
  • Macrophages even eat iron filings and carbon particles
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14
Q

Describe the role of antigen presenting cells (APC) in relation to T cells

A
  • T cells need help to recognise antigens
  • T cells cannot ‘see’ native, soluble, intact proteins
  • ‘Professional APC’ include dendritic cells, which present antigens to T cells
  • They communicate what kind of damage the pathogen is causing and what needs to be done to combat the threat
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15
Q

What are the two types of MHC, Major Histocompatability complex? (how APCs in humans present their antigens):

A
  • Class I and Class II
  • MHC Class I – expressed on every cell that has a nucleus (RBC’s do not express MHC)
  1. Only seen by cytotoxic T cells
  2. Tells the cytotoxic T cells what’s going on inside the cell (healthy or infected with a virus)
  • MHC Class II – designed to present antigens taken from outside the cell (ectracellular environment)
  • expressed by antigen presenting cells: macrophages, B cells and dendritic cells
  1. Only seen by helper T cells
  2. Tells helper T cells what kind of response is needed
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16
Q

Immune system strategies: The adaptive immune system

A
  • The third level of defence
  • Called ‘adaptive’ because it generates a specific response to a given pathogen
  • Slower than the innate response, but more powerful
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17
Q

Give examples of the adaptive immune system

A

Cytotoxic T cells, Helper T cells and B cells

18
Q

What are the functions of Cytotoxic T cells?

A

They recognise specific invaders and kill specific virus-infected cells

19
Q

What are the function of Helper T-cells?

A

Helper T cells coordinate the response usually through signalling and sometimes through cell-cell contact

20
Q

What are the functions of B cells?

A

B cells produce sophisticated antibodies that remember, seek out and destroy invaders

21
Q

Describe the activation of adaptive immunity

How many signals are needed for activation?

A
  • B cells and T cells need to be regulated, so they must be activated before they can function
  • For many aspects of adaptive immunity, a two signal system is adopted
  • For naïve T cells to interact with the dendritic cells, these two signals are:
  1. antigen-specific: T cell receptor recognises antigen form the pathogen presented in MHC on APC
  2. non-specific: B7 molecules on APC bind to CD28 on T cell
22
Q

Explain Edward Jenner and the smallpox vaccine (1796)

A
  • Smallpox was a major health problem (up until it was eradicated in 1979)
  • Estimated to have killed 300-500 million people during the 20th century alone
  • Jenner realised that milkmaids often got cowpox, but not smallpox
  • Cowpox symptoms are like smallpox but less severe
  • So Edward Jenner injected cowpox pus into a boy

o(cow = vacca - vaccine)

  • Then Jenner infected the boy with smallpox
  • The boy didn’t get smallpox!
  • His adaptive immune response protected him
  • But he was only protected against the pox virus - adaptive immunity is SPECIFIC to the invader
23
Q

How are Antibodies multi-functional molecules?

A
  • Stick to pathogens
  • Precipitate pathogens
  • Neutralize pathogens
  • Eliminate infected cells
  • Opsonize pathogens (tagged for destruction\ enhances phagocytosis by marking an antigen for an immune response or marking dead cells for recycling)
24
Q

What happens to antibodies during bacterial invasion?

A

Antibody Fab regions bind to the invaders and antibody Fc regions bind macrophages - antibodies act as bridges

25
Q

What are the main classes of lymphocytes (cells of the adaptive immune system)?

What are they derived from?

A
  • Lymphocytes (B cells and T cells):
  • B cells
  • Cytotoxic Tc cells
  • Helper TH cells
  • Reguatory Treg cells

All derived from same stem (lymphoid progenitor) cells found in the bone marrow

26
Q

Lymphocytes: What are the function of B cells?

A

produce antibodies

27
Q

Lymphocytes: What are the functions of cytotoxic Tc cells?

A

Seek out and destroy virus-infected cells

28
Q

Lymphocytes: What are the functions of helper TH cells?

A

produce signals to initiate and maintain an appropriate adaptive immune response

29
Q

What turns on an immune response? The danger hypotheis

A
  1. There is an invader (danger signal, evidence of damage etc)
  2. Dendritic cells survey the damage and collect information
  3. Then inform T cells, who coordinate an appropriate response
30
Q

What are Secondary lymphoid organs?

A
  • Where the immune response is coordinated
  • For adaptive immunity to be activated, the T cells specific for the invader needs to see the dendritic cells that had previously encountered the same invader… unlikely over the whole body area
  • Secondary lymphoid organs make these encounters more likely
31
Q

Mammals have two plumbing systems:

A
  • Cardiovascular system

pressurized

pumps blood round the body

  • Lymphatic system

not pressurized

drains tissue fluid that leaks out of capillaries

32
Q

What is the function of the lymphatic system?

A
  • Lymph collects in lymphatic vessels and is transported back to the blood, via the lymph nodes
  • Lymph collects proteins, cells etc. from the tissue
33
Q

Explain the role of the lymphatic system in immune respones

A
  • Immune response coordinated at lymph node near the targer area (secondary lymphoid organ)
  • Antigens from bacteria and viruses get carried from the site of infection to the lymph nodes via the lymph
  • APC, T cells and B cells travel to the lymph nodes
  • Increases the probability that the lymphocyte will encounter antigen/APC and be activated
34
Q

Why do we need both innate and adaptive immune systems?

A
  • Innate – fast and effective, but not specific
  • Adaptive – slower, but tailored to fit
  • Innate immune system informs the adaptive immune system
  • Innate immunity integrates the response
  • It tells either B cells or T cells to react depending on the invader and where they should go to find the invader
35
Q

Summarise the lecture

A
  • Three lines of defence – physical barriers, innate immunity, adaptive immunity
  • Macrophages are the primary cells of innate immunity
  • Dendritic cells detect and interpret danger, then inform T cells
  • T and B cells are the primary cells of adaptive immunity
  • Antibodies, made by B cells, are the molecules of adaptive immunity
  • T cells need the help of MHC on APCs to ‘see’ antigen
  • Cell encounters occur in specialised lymphoid tissue
  • Lymph percolates through the tissues, collecting cells and antigens
  • Adaptive immunity has specific memory to protect us against subsequent infections

Mistakes can be made in immune responses – these are rare but devastating (autoimmunity, allergy, cancer, immunosuppression)

36
Q

How does the immune system protect the body from pathogens?

A
  1. Physical response
  2. Innate response
  3. Adaptive immune response
37
Q

How do APC’s preset their antigens in mice?

How do APC’s present their antigens in humans?

A

In mice:

  • major histocompatibility complex (MHC)
  • in humans:

human leukocyte antigen (HLA)

38
Q

Why do RBC’s not express MHC (class 1)?

A

MHC class I specifically present antigens from viruses and virsuses need a nucleus to take over in order to infect the cell

39
Q

Do cytotoxic T cells do the same job as natural killer cells?

A

Yes

It just takes cytotoxic T cells longer and they are more specific

40
Q

Which part of the immune system take a lot of energy to generate, when they search and proliferate?

A

Adaptive immune system

41
Q

Describe the structure of antibodies

A
  • Consists of a heavy (inside) and a light chain (outside)
  • Effector function region/ constant fragent (FC) at one end of the antibody, for every class of antibodies, this region is the same.
  • Different cells e.g. macrophages have receptors on their surface that recognise FC regions that allows the antibody to attach
  • Antigen binding fragent (Fab) at the other end of the antibody, this is where the antigens bind. The molecular sequence is always different here
42
Q

What are the function of Treg cells?

A
  • put the brakes on when the danger has passed
  • prevents self reactivity

Immunology (BY1IM1) (11 decks)

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