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Principles > Immunology > Flashcards

Immunology Flashcards

1
Q

Describe the evolutionary arms race between pathogen and host

A

Pathogen exploits flaws in the defensive barriers of its host
The host evolves to correct those flaws
Pathogen replicates and evolves to evade corrections to exploit other flaws
Pathogen has ability to replicate much faster than the host; host relies on flexible and rapid immune response to combat

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2
Q

Some features of skin that contribute to barring infection include…

A

Tightly packed keratinised cells undergo renewal constantly; limits colonisation
Low pH kills pathogens
Sebaceous glands secrete oils and enzymes to destroy bacterial cell walls

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3
Q

The innate immune system has a ___ response and is ____ to micro-organisms

A

Fast, non-specific

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4
Q

The adaptive immune system has a ___ response and is ____ to micro-organisms

A

Slow, specific

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5
Q

The 5 types of leukocytes (WBCs)?

A

Neutrophils, Monocytes, Lymphocytes, Eosinophils, Basophils + Mast cells

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6
Q

Define Primary lymphoid tissue (with examples)

A

Anatomical sites where WBCs are produced

Bone marrow, thymus

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7
Q

Define Secondary lymphoid tissue (with examples)

A

Involved in filtering extracellular fluids and activating cells of the adaptive immune response

Spleen, tonsils, lymph nodes, Peyer’s patches and mucosa-associated lymphoid tissue (MALT)

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8
Q

List the leukocyte components of the innate immune system

A

Macrophages, neutrophils, dendritic cells, basophils, mast cells, eosinophils, NK cells

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9
Q

List the soluble components of the immune system

A

Antibodies
Complement
Cytokines (interferons, TNFalpha, chemokines and interleukins)

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10
Q

Basophils and mast cells mature in bone marrow. True/false?

A

False

Basophils mature in bone marrow; mast cells mature once in tissue

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11
Q

Basophils and mast cells are mainly involved in ____. They secrete ____, leading to _____…

A

Allergic reactions

Secrete histamine and inflammatory mediators, leading to increased vascular permeability and smooth muscle contraction

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12
Q

The main function of phagocytes is?

A

“Eat” cells by ingesting them and mopping up debris

Neutrophils, macrophages and dendritic cells mainly involved in phagocytosis

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13
Q

PRRs recognise what on bacteria/viruses?

A

PAMPs

Not expressed by human cells

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14
Q

Opsonins enhance…

A

Phagocytosis

Act as a bridge between pathogen and phagocyte receptors

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15
Q

Major opsonins include…

A

C3b, collectins, Fc of IgG, CRP

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16
Q

Oxidative killing requires which crucial enzyme?

A

NADPH oxidase complex

Converts oxygen into reactive free radicals

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17
Q

Acute phase proteins are produced by…

A

The liver

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18
Q

CRP greater than 200mg/l indicates…

A

Severe bacterial/fungal infection

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19
Q

The function of cytokines is to…

A

Modulate the behaviour of immune cells, locally and systemically

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20
Q

Interferons are important in…

A

Limiting viral infections

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21
Q

Interleukins are important in…

A

Directing cells to divide/differentiate

Mainly produced by T cells (IL-2 important for T cell activation)

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22
Q

Chemokines are important in…

A

Establishing a concn gradient to direct movement of cells (tell leukocytes where to go)

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23
Q

Complement involves enzymatically activating proteins in a…

A

Biological cascade, resulting in a rapid response

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24
Q

With regard to complement activation;

Classical pathway is activated by…

A

Fc region of antibodies (so B cells need to have been activated for this) such as IgG/IgM which cause conformational change in C1, activating cascade

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25
Q

With regard to complement activation;

In the classical pathway, first C1 is activated, then…

A

C4, C2, C3

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26
Q

With regard to complement activation;

Mannose-binding Lectin pathway is activated by…

A

MBL protein (produced in liver) recognises and binds Mannose on bacteria

This mimics binding of C1 to immune complexes, so there is no need for antibodies

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27
Q

With regard to complement activation;

Alternate pathway is activated by…

A

Spontaneous hydrolysis of C3 via C3b positive feedback and its direct binding to bacterial cell walls

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28
Q

Membrane attack complex is assembled by which complement proteins?

A

C5-C9

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29
Q

Functions of C3a and C5a

A

Anaphylatoxins - Inflammatory mediators - activate mast cells (causing degranulation) and act directly on local blood vessels

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30
Q

Examples of complement inhibitors

A

C1, Factor I, Factor H, C4 binding protein, CD59

31
Q

List the leukocyte components of the adaptive immune system

A

B lymphocytes, T lymphocytes

32
Q

List the protein components of the adaptive immune system

A

Antibodies, cytokines

33
Q

Antibodies act as opsonins. True/False?

A

True - especially IgG

34
Q

Antibodies are Y shaped glycoproteins made up of…

A

Two heavy chains and two light chains

Heavy chains have variable regions; light chains have constant regions

35
Q

List the immunoglobulins found in the blood, from most to least abundant

A

IgG, IgA, IgM, IgD, IgE

36
Q

Main functions of IgG

A 
Agglutination
Complement activation 
Neutralisation 
Opsonisation 
NK cell activation
Provides antibody-mediated immunity to developing foetus and neonates
37
Q

Main functions of IgA

A

Secretory; found in breast milk, saliva, tears

Defence at mucosal surfaces via neutralisation

38
Q

Main functions of IgM

A

Found in plasma as a pentamer; first Ig produced during infection

Membrane-bound form - serves as BCR to activate B cells
Agglutination
Complement system activation

39
Q

Main functions of IgD

A

Membrane-bound form serves as BCR (like IgM)

Unknown; protection against URT infections

40
Q

Main functions of IgE

A

Role in allergic reactions activating mast cells (causing degranulation)

41
Q

T cell antigen receptors can recognise free antigens. True/False?

A

False

Need to be presented as a complex with MHC molecules usually by dendritic cells

42
Q

MHC I presents to?

A

CD8+ T cells

Expressed on all nucleated cells

43
Q

MHC II presents to?

A

CD4+ T cells

Expressed only on antigen presenting cells (dendritic cells, B cells, macrophages)

44
Q

T cell activation requires…

A

MHC binding to T-cell receptor

Dendritic cell B7 binding to CD28 on T cells

45
Q

B cell activation requires…

A

Antigen binding to B-cell receptor (IgM or IgD)
PRRs recognising PAMPs
Optional co-stimulation by Follicular Helper T (CD4+) cells through CD40L

46
Q

Function of IL-2

A

T cell proliferation, activation and differentiation

47
Q

Function of IL-4, IL-5 and IFNy

A

Activate B cells; increase killing

48
Q

Name some pro-inflammatory cytokines

A

IL-1
IL-6
TNFalpha

49
Q

What effect do pro-inflammatory cytokines such as IL-6 have on the liver?

A

Stimulate release of acute phase proteins (CRP, C3…)

50
Q

Which cytokines are responsible for restoration of homeostasis after an infection?

A

IL-10 released by macrophages is an anti-inflammatory cytokine

51
Q

What cytokines do macrophages release and what are their roles?

A

TNFalpha - vasodilation
IL-1 - pro-inflammation
IL-10 - anti-inflammation

52
Q

Which tissues do not have a lymphatic drainage?

A

Cartilage and epidermis

53
Q

Lymph vessels have valves. True/False

A

True

54
Q

Which WBCs arise from granulocyte precursor cells?

A

Neutrophils, Eosinophils, Basophils

55
Q

What is the common precursor to macrophages and dendritic cells?

A

Monocytes

56
Q

Which cells arise from lymphoid progenitor cells?

A

NK cells, T cells and B cells

57
Q

What is the role of NK cells?

A

Kill virally infected cells, antibody-bound cells and tumour cells

They also release IFN gamma which enhances macrophage killing

58
Q

What effect does IFNgamma have on macropahges?

A
  • increased ROS-mediated killing

- increased antigen presenting ability

59
Q

What substances do mast cells release when they degranulate?

A

Histamine, TNFalpha, LTs and PGs

60
Q

What do mast cells protect against?

A

Large antibody coated pathogens that cannot be phagocytosed

61
Q

Describe the two mechanisms by which neutrophils kill pathogens

A

Phagolysosomal Killing

  • Lysozyme - degrade cell wall of some gram positive bacteria
  • Acidification - bactericidal or bacteriostatic
  • Lactoferrin - Fe binding protein (starves bacteria of iron)
  • Acid Hydrolyases - further digest bacteria

ROS-mediated killing
- NADPH oxygenase-dependent mechanisms

62
Q

What are do neutrophil extracellular traps (NETs) do?

A

Released in to ECF by neutrophils to immobilise pathogens

63
Q

T cells can only recognise _____ antigens

A

Peptide

64
Q

Which immunoglobulins form BCR in their membrane bound state?

A

IgM and IgD

65
Q

Describe the process of neutrophilic transendothelial migration

A

Margination of neutrophils to the endothelium near sites of damage
Neutrophils weakly bind endothelial cells via adhesion molecules (selectins, ICAM-1) which are upregulated due to TNFalpha and histamine
Migration of neutrophils across endothelium via diapedesis
Movement of neutrophils within ECF via chemotaxis
Activation of neutrophils via PRR-PAMP binding and TNFalpha

66
Q

Which cell in the innate immune system is most responsible for TNFalpha production and pathogen killing and degradation?

A

Neutrophils

67
Q

How do virally-infected cells behave?

A

Release IFNalpha/beta to prevent virus replication and also attract T cells by upregulating MHC-I on neighbouring cells
Virally-infected cells have less MHC therefore is targeted by NK cells

68
Q

What is the second Ig produced in the initial immune response?

A

IgG

69
Q

Which Ig has the longest half life?

A

IgG - therefore ideal for neonatal immunity before child develops adaptive immunity

70
Q

What is transient hypogammaglobulinaemia of the newborn?

A

Period of susceptibility where maternal IgG weans off and neonatal adaptive immune system is still developing

71
Q

How does IgG act as an opsonin?

A

Phagocytes express Fc-gamma receptors that bind IgG Fc regions

72
Q

What type of cells do THO differentiate into?

A

TH1, TH2, TFH, Regulatory T cells

73
Q

What is the role of TH1 cells?

A

Secrete pro-inflammatory cytokines that enhance macrophage ROS-mediated killing

74
Q

What is the role of TFH cells?

A

Move to B cell region within lymph node to restimulate MHC-II on B-cells
They then proliferate and differentiate into either plasma cells or memory B cells

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