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BIOMOLECULES AND CELLS > Immune System > Flashcards

Immune System Flashcards

1
Q

Pathogens

A

Harmful organisms and viruses that can cause disease.

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2
Q

Immunity

A

The ability to avoid disease when invaded by a pathogen

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3
Q

Innate immunity

A

Involves recognising components that are common to many pathogens
• Non-specific
• typically a very rapid response

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4
Q

Adaptive immunity

A

Involves recognising components that are specific to each particular pathogen
• specific
• can distinguish bw healthy, abnormal and non-self cells
• typically slow to develop and longer lasting

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5
Q

Phagocytosis

A

Ability to eat/engulf pathogens, apoptotic or necrotic/dead cells.

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6
Q

Examples of cells in innate immunity

A
  • Macrophage
  • Complement proteins
  • Mast cells
  • leucocyte (WBCs)
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7
Q

Examples of cells in adaptive immunity

A 
• B-cell
• Antibodies
T cells
• helper cells
• cytotoxic cells

B and T cells are lymphocytes (type of white blood cell)

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8
Q

Formation and development of B and T cells.

A

B cells develop and mature in the bone marrow.
Then circulate in blood and lymph.

T cells develop in the bone marrow and then migrates to the thymus to develop.

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9
Q

Function of the lymph nodes

A
  • Small, round structures at many sites along the lymph vessels.
  • As lymph passes through the nodes, it is filtered and ‘inspected’ for non-self
  • contain many WBCs (lymphocytes)
  • connected to one another by lymph vessels
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10
Q

Difference between lymph and plasma

A
  • Plasma: contain both white and red blood cells

* Lymph: contains no red blood cells

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11
Q

Macrophages role

A

Have function in the innate and adaptive immune system

  • engulf and digest pathogens, infected cell, cellular debris
  • use defensins to kill pathogens after engulfing them
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12
Q

Where are mast cells found?

A
  • Found in surrounding blood vessels and nerves in the connective tissue of most organs
  • In the boundaries between the internal and external environment
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13
Q

What do macrophages secrete?

A

Defensins

- nitric oxide

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14
Q

What do mast cells secrete?

A
  • Histamines
  • prostaglandins
  • Tumor necrosis factor
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15
Q

What is the complement system?

A
  • Specialised proteins involved in both innate and adaptive immune systems
  • more than 20 diff. proteins
  • mostly made in the liver
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16
Q

What is the mode of action of complements?

A
  1. Chemotaxis - Attract phagocytes to an injured area
  2. Attach to antigens on pathogen surface or to an antibody bound to a pathogen - this helps phagocytes to recognise and kill pathogens
  3. lead to lysis (break down) of cells
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17
Q

1st line of defence

A

Skin, mucus, cilia, chemicals (lysosome), flora.

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18
Q

2nd line of defence

A

Phagocytes, complement, interferons, inflammation, fever, mast cells.

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19
Q

Why is inflammation painful?

A

• Increased pressure of prostaglandins released from mast cells - this increases the sensitivity of pain receptors.

Aspirin relieves pain by blocking synthesis of prostaglandins.

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20
Q

Allergic reactions

A
  • non-self molecule that is normally harmless binds to mast cell
  • mast cells release histamines
  • inflammation causes itchy/watery eyes
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21
Q

Autoimmune disease

A

Immune system fails to distinguish between self and non-self and attacks tissues in the body

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22
Q

Sepsis

A
  • A bacterial infection caused by damage to body (ie. cut, splinter, wound)
  • does not stay localised to one area and spreads throughout the body and dilation of blood vessels also spreads
  • this leads to drop in blood pressure - can be lethal
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23
Q

Why is exercise important for the functioning of the immune system?

A

Lymph is not pumped around like blood, it moves through vessels by body movements. (ie contraction of skeletal muscles).

Lymph also transports dietary fats and lipid-soluble vitamins

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24
Q

What is oedema?

A

A condition characterised by an excess of watery fluid collecting in the cavities or tissues of the body.

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25
Q

Oedema due to inflammation

A
  • Increased blood flow due to dilation of blood vessels supplying the region of injury
  • paracrine factors like histamine cause increases permeability of capillaries
  • fluid and blood proteins move to the interstitial space - oedema
26
Q

Proteins in the adaptive immune system?

A
  • Antibodies (B cells)
  • T-cell receptors (T cells)
  • MHC
  • Cytokines
27
Q

Function of cytokines and what cells secretes it?

A
  • secreted by T helper cells.

* via specific receptors they activate or inhibit B-cells, macrophages, T-cells

28
Q

Define antigen

A

A molecule that interacts with specific receptors on T-cells and B-cells.
• for B cells, receptors is a membrane bound antibody

29
Q

Define antigenic determinant (epitope)

A

The specific region on an antigen that is recognised by a specific antibody or T-cell receptor.
• one antigen can have many antigenic determinants

30
Q

Immunogens

A

Substances that trigger a response from the immune system

31
Q

Differentiate between immunogens and antigens

A
  • Not all antigens produce an immunogenic response

* ALL immunogens are antigens

32
Q

What are 4 key features of the adaptive immune system?

A
  1. Specificity
    Antibodies and T-cell receptors bind to specific antigens
  2. Ability to distinguish self from non-self (using MHC)
  3. Diversity
    Humans can make millions of different antibodies and T-cell receptors
  4. Immunological memory (memory cells)
33
Q

Describe the HUMORAL immune response

A
  • response employs antibodies secreted by plasma cells to target antigens in body fluids
  • involves antibodies and B cells
34
Q

Describe the CELLULAR immune response

A
  • employs T cells to attack body cells that have been altered by viral infection or mutation
  • or to target antigens that have invaded the body’s cells
  • involves T cells and T cell receptors
35
Q

How many polypeptide chains make up an antibody?

A
  • 4 chains: 2 light, 2 heavy
36
Q

What bond holds the light and heavy chain in an antibody?

A

disulfide bonds

37
Q

How are antibodies specific?

A

Light and heavy chains contain variable regions.

Each variable region is specific for ONE antigen.

38
Q

What does bivalent mean in terms of antibodies?

A

Each antibody has 2 identical binding sites for antigens that are the same.
- Antigens bind in the antigen binding region via their antigenic determinants

39
Q

What are the 2 types of B-cells?

A
  1. Plasma cells - secrete antibodies (SHORT acting)

2. Memory cells have membrane bound antibodies (LONG acting)

40
Q

Function of B memory cells?

A
  • their membrane antibodies bind to pathogens
  • Complex is then endocytosed
  • activation of memory B cells
  • production and secretion of more antibodies
41
Q

What are the 2 types of T cells?

A
  1. T-helper cells - assist both humoral and cellular

2. T cytotoxic cells

42
Q

What do T helper cells do?

A

T-helper cells respond by producing cytokines that direct the action of other cells (B cells, Tc, macrophages)

43
Q

What do Tc cells do?

A

Tc cells respond by releasing perforins that lyse the infected and abonormal cells.

44
Q

Describe the structure of an MHC molecule.

A
  • made up of 2 polypeptide chains (alpha and beta)

- Variable region of the 2 peptide chains direct specificity of the antigen binding site.

45
Q

Where are MHC molecules found?

A

Found on all cells.

  • Most cells have MHC class I.
  • B cells, macrophages and dendritic cells have MHC class II.
46
Q

What do Antigen Presenting cells do?

A
  1. Macrophage takes up antigen
  2. Breaks down antigen into fragments
  3. A class II MHC molecule binds antigen fragment and carries it to the membrane
  4. MHC ‘presents’ the antigen to a T-helper cell
47
Q

How does antibody binding promote phagocytosis?

A
  • Antibodies bind to antigenic determinants on bacteria
  • Macrophages have receptors for the constant region of the heavy chains of the antibody
  • Binding of antibody to macrophage receptor activates phagocytosis
48
Q

What are MHC molecules?

A

Membrane bound glycoproteins that direct recognition of self from non-self.

49
Q

MHC Class I proteins

A

Found on all nucleated cells

  • When a normal cells becomes infected or abnormal, it displays pathogen on MHC class I
  • Tc cells recognise cells as non-self
50
Q

MHC Class II proteins

A

Found on macrophages, B-cells and dendritic cells

- Present pathogen to Th cells

51
Q

What is the difference between MHC class I and II?

A

Class I

  • on all nucleated cells
  • present antigen to Tc cells

Class II

  • macrophages, dendritic, B-cells and APCs
  • present to T-helper cells
52
Q

How is the adaptive immune system diverse?

A

B and T cells can ‘make’ new gene combinations to create millions of different variable regions in Antibodies and T-cell receptors.

53
Q

Clonal selection

A
  • Antigens presented to the immune system trigger the proliferation of lymphocytes (T and B)
  • Lymphocytes proliferate and generate a clone of genetically identical cells
54
Q

Clonal deletion

A

During early differentiation, immature B or T cells that have the potential to cause an immune response agains self-antigens, undergoes programmed cell death.

55
Q

Formation of memory B cells

A
  • Antigens binding and T-H cell signalling selects a B cell for proliferation
  • This B cells forms a colont of effector and memory cells
  • Effector cells produce antibodies
56
Q

Immunisation

A
  • Natural

- Exposure to disease-causing pathogen provides natural immunity (memory B and T cells)

57
Q

Vaccination

A
  • Artificial
  • Introduces an attenuated pathogen that does not cause disease
  • immune system forms B and T memory cells
58
Q

What responses occur after a vaccination?

A
  1. primary immune response - number of responding immune cells is low (Vaccine response)
  2. protective response to pathogen is faster and stronger
59
Q

Humoral immunity

A
  1. Cell with surface antigen
  2. APC presents antigen to T-H cell
  3. T-H cell stimulates B cell which either binds to free antigens or produces antibodies
  4. antibodies either bind to free antigens or to the cells with surface antigen
60
Q

Cellular immunity

A
  1. Cell with surface antigen
  2. APC presents antigen to T-H cell
  3. T-H cell stimulates Tc cell to kill all cells with foreign antigens
61
Q

First and second line of defence action

A

1st: 0-4 hours
- infection recognised by phagocytes

2nd: 4-96 hours
- Recruitment of effector cells (e.g. macrophages)

Both involve the innate immune system

62
Q

3rd line of defence action

A

96- hours

  • Adaptive immunity
  • Transport of antigens to lymphoid organs, for recognition by T and B cells and proliferation of these cells

BIOMOLECULES AND CELLS (32 decks)

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