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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
With regard to complement activation; In the classical pathway, first C1 is activated, then...
C4, C2, C3
26
With regard to complement activation; Mannose-binding Lectin pathway is activated by...
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
27
With regard to complement activation; Alternate pathway is activated by...
Spontaneous hydrolysis of C3 via C3b positive feedback and its direct binding to bacterial cell walls
28
Membrane attack complex is assembled by which complement proteins?
C5-C9
29
Functions of C3a and C5a
Anaphylatoxins - Inflammatory mediators - activate mast cells (causing degranulation) and act directly on local blood vessels
30
Examples of complement inhibitors
C1, Factor I, Factor H, C4 binding protein, CD59
31
List the leukocyte components of the adaptive immune system
B lymphocytes, T lymphocytes
32
List the protein components of the adaptive immune system
Antibodies, cytokines
33
Antibodies act as opsonins. True/False?
True - especially IgG
34
Antibodies are Y shaped glycoproteins made up of...
Two heavy chains and two light chains | Heavy chains have variable regions; light chains have constant regions
35
List the immunoglobulins found in the blood, from most to least abundant
IgG, IgA, IgM, IgD, IgE
36
Main functions of IgG
``` Agglutination Complement activation Neutralisation Opsonisation NK cell activation Provides antibody-mediated immunity to developing foetus and neonates ```
37
Main functions of IgA
Secretory; found in breast milk, saliva, tears | Defence at mucosal surfaces via neutralisation
38
Main functions of IgM
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
Main functions of IgD
Membrane-bound form serves as BCR (like IgM) Unknown; protection against URT infections
40
Main functions of IgE
Role in allergic reactions activating mast cells (causing degranulation)
41
T cell antigen receptors can recognise free antigens. True/False?
False | Need to be presented as a complex with MHC molecules usually by dendritic cells
42
MHC I presents to?
CD8+ T cells | Expressed on all nucleated cells
43
MHC II presents to?
CD4+ T cells | Expressed only on antigen presenting cells (dendritic cells, B cells, macrophages)
44
T cell activation requires...
MHC binding to T-cell receptor | Dendritic cell B7 binding to CD28 on T cells
45
B cell activation requires...
Antigen binding to B-cell receptor (IgM or IgD) PRRs recognising PAMPs Optional co-stimulation by Follicular Helper T (CD4+) cells through CD40L
46
Function of IL-2
T cell proliferation, activation and differentiation
47
Function of IL-4, IL-5 and IFNy
Activate B cells; increase killing
48
Name some pro-inflammatory cytokines
IL-1 IL-6 TNFalpha
49
What effect do pro-inflammatory cytokines such as IL-6 have on the liver?
Stimulate release of acute phase proteins (CRP, C3...)
50
Which cytokines are responsible for restoration of homeostasis after an infection?
IL-10 released by macrophages is an anti-inflammatory cytokine
51
What cytokines do macrophages release and what are their roles?
TNFalpha - vasodilation IL-1 - pro-inflammation IL-10 - anti-inflammation
52
Which tissues do not have a lymphatic drainage?
Cartilage and epidermis
53
Lymph vessels have valves. True/False
True
54
Which WBCs arise from granulocyte precursor cells?
Neutrophils, Eosinophils, Basophils
55
What is the common precursor to macrophages and dendritic cells?
Monocytes
56
Which cells arise from lymphoid progenitor cells?
NK cells, T cells and B cells
57
What is the role of NK cells?
Kill virally infected cells, antibody-bound cells and tumour cells They also release IFN gamma which enhances macrophage killing
58
What effect does IFNgamma have on macropahges?
- increased ROS-mediated killing | - increased antigen presenting ability
59
What substances do mast cells release when they degranulate?
Histamine, TNFalpha, LTs and PGs
60
What do mast cells protect against?
Large antibody coated pathogens that cannot be phagocytosed
61
Describe the two mechanisms by which neutrophils kill pathogens
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
What are do neutrophil extracellular traps (NETs) do?
Released in to ECF by neutrophils to immobilise pathogens
63
T cells can only recognise _____ antigens
Peptide
64
Which immunoglobulins form BCR in their membrane bound state?
IgM and IgD
65
Describe the process of neutrophilic transendothelial migration
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
Which cell in the innate immune system is most responsible for TNFalpha production and pathogen killing and degradation?
Neutrophils
67
How do virally-infected cells behave?
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
What is the second Ig produced in the initial immune response?
IgG
69
Which Ig has the longest half life?
IgG - therefore ideal for neonatal immunity before child develops adaptive immunity
70
What is transient hypogammaglobulinaemia of the newborn?
Period of susceptibility where maternal IgG weans off and neonatal adaptive immune system is still developing
71
How does IgG act as an opsonin?
Phagocytes express Fc-gamma receptors that bind IgG Fc regions
72
What type of cells do THO differentiate into?
TH1, TH2, TFH, Regulatory T cells
73
What is the role of TH1 cells?
Secrete pro-inflammatory cytokines that enhance macrophage ROS-mediated killing
74
What is the role of TFH cells?
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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