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POM 4 Immunology > 4.13 Immune Response to Infection > Flashcards

4.13 Immune Response to Infection Flashcards

1
Q

What are the 4 different pathogen niches during infection?

A

Extracellular – bacteria

Surface adherent – enteropathogenic and enterohaemorrhagic e. coli

Intracellular vacuolar – salmonella, chlamydia, plasmodium, legionella

Intracellular cytosolic – viruses, listeria, bukholderia, mycobacteria

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2
Q

How does an immune response to infection start?

A

Tissue damage occurs
Microbe is detected
Intracellular signalling occurs, leading to interleukin production
Thus the adaptive immune response is primed

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3
Q

How does an immune response to infection end?

A

Pathogen is cleared
Production of inflammatory cytokines is stopped
Tissue repair and remodelling occurs
Memory cells are developed

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4
Q

What are the 3 broad differences between innate and adaptive immunity?

A

Innate – fast acting, first line of defense, germline encoded receptors

Adaptive – slow but long lasting, physical barrier, variable receptors

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5
Q

Give examples of physical barriers provided by innate immunity

A

Epithelial cells
Skin
Mucosa

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6
Q

Is complement part of innate or adaptive immunity?

A

Both

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7
Q

What are the key cellular components of innate immunity?

A

Granulocytes, macrophages, dendritic cells, NK cells

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8
Q

What are the humoral components of innate immunity?

A

Complement, lectins, pentraxins, antimicrobial peptides

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9
Q

What are the key cellular components of adaptive immunity?

A

T cells (killer, reg, helper), B cells, plasma cells

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10
Q

What are the humoral components of adaptive immunity?

A

Antibodies and complement

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11
Q

What is the difference in specificity between innate and adaptive immunity?

A

Innate is less specific – it detects broad pathogen classes via PAMPs

Adaptive is specific – it detects structural details of antigens and non-microbial antigens

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12
Q

What is the major difference between innate and adaptive immunity receptors?

A

Adaptive immunity receptors have a greater diversity

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13
Q

Why is there a greater diversity in adaptive immune receptors in comparison to innate immune receptors?

A

Adaptive immunity receptors are encoded by genes produced from somatic recombination

This produces TCRs and Ig’s with many variations

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14
Q

What do adaptive and innate immunity both provide to the body?

A

Humoral and cellular response

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15
Q

List the general sequence of molecular and cellular events of an immune response?

A

Microbe is detected
Naive host cell undergoes gene expression changes and is activated
Antimicrobial molecules are produced and communicate to nearby cells
This produces an activated and specialised host cell

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16
Q

What are the first responders to site of injury?

A

Neutrophils, then monocytes that differentiate into macrophages

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17
Q

What do neutrophils and macrophages do when responding to a site of injury?

A

Naive cells become activated when interacting with microbes

Phagocytes control infection and limit tissue damage

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18
Q

What can uncontrolled activities of first responders lead to?

A

Excessive inflammation
Tissue damage
Granulomas

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19
Q

How do phagocytes and other immune cells identify bacteria?

A

Cell wall components (e.g. LPS)

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20
Q

How do phagocytes and other immune cells identify fungi?

A

Dectin-1 on phagocytes recognise beta glucans on fungi and signal through SRC tyrosine kinases

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21
Q

How do phagocytes and other immune cells identify viruses?

A

Viral DNA/RNA in cytoplasm

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22
Q

How does live vs dead bacteria elicit different immune responses?

A

Live bacteria causes production of inflammatory cytokines, metabolic genes, antimicrobial genes and immunomodulatory genes

Dead bacteria results in resolution of inflammation

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23
Q

What are the common cell surface molecules unique to fungi?

A

Beta glucans

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24
Q

What type of immune response do fungi produce?

A

Production of inflammatory cytokines, antimicrobial, metabolic and immunomodulatory genes

25
Q

What type of immune response do viruses produce?

A

Production of inflammatory cytokines, antiviral genes, immunomodulatory genes, and interferons

26
Q

What do interferons do?

A

Binds IFNRs to activate the anti viral state of the cell

Gene transcription occurs to block viral replication, producing 2’5’ oligoadenylate synthetase and protein kinase R

27
Q

What do activated macrophages show?

A

Enhanced:
Phagocytosis and migration
Cytokine/chemokine production
Cell surface molecule expression
Antimicrobial activity
Antigen presentation and T cell activation

28
Q

Against which 2 classes of pathogens are interferons active?

A

Viruses and gram negative bacteria

29
Q

What are type I IFNs produced by, and what do they do?

A

All primary infected cells (mainly plasmacytoid DCs)

Promote antiviral response

30
Q

What are type II IFNs produced by, and what do they do?

A

Lymphocytes only

Promote antibacterial response

31
Q

What are type III IFNs produced by, and what do they do?

A

Epithelial cells

Promote antiviral response

32
Q

What do antiviral genes include?

A

Nucleases
Inhibition of viral entry and exit
Inhibition of uncoating and replication
Inhibition of viral protein translation

33
Q

What are the immunomodulatory roles of IFNs?

A

Enhance T cell actions
Anti inflammatory response
Tissue repair

34
Q

How are virus-infected cells killed?

A

CD8 T cells or NK cells

35
Q

What does cell death remove?

A

Viral replicative niches

36
Q

Give 2 antimicrobial enzymes that are produced by a cytokine binding to a cytokine receptor leading to the killing of microbes?

A

Phagocyte oxidase – produces ROS

Inducible nitric oxide synthase – produces NO

37
Q

What are the soluble effector mechanisms of innate immunity?

A

Complement mediated destruction
Lectin binding for neutralisation
Iron chelation (siderophores) to prevent replication
Antibiotic like peptide production

38
Q

What are the cellular effector mechanisms of innate immunity?

A

ROS and NO from phagocyte oxidase and inducible nitric oxide synthase

Acidification and digestion within phagosomes

39
Q

How are T cells activated?

A

Activated APCs present antigens on MHC to T cells

APCs produce cytokines for T cell activation, such as IL-12 for T cell replication

T cells produce cytokines that activate phagocytes, such as IFN-gamma that upregulates MHC II expression

Cytokines also act in an autocrine manner, such as IFN-gamma causing differentiation into Th1 and IL-17 causing differentiation into Th17

40
Q

How are dendritic cells better able to respond to viral infections than macrophages?

A

Dendritic cells produce more type I interferons (a, B) during infection

41
Q

How do T cells help B cells produce antibodies?

A

T helper cells activate B cells with the correct BCR specific to the original antigen

42
Q

What are Th and Tc cells produced in response to respectively?

A

T helper – bacterial infections, produces cytokines
T killer – viral infections, removes viral replicating niches

43
Q

What are some T cell functions?

A

Phagocyte activation
B cell activation
Direct killing of infected cells
Innate lymphoid cells (gamma-delta T cells in mucosa)

44
Q

What class of T helper cells do macrophages produce and how?

A

Macrophages respond to intracellular pathogens by producing IFN-gamma

This causes differentiation of T cells into Th1

45
Q

What class of T helper cells do eosinophils produce and how?

A

Eosinophils respond to parasitic infection

Release of IL4, 5, and 13 cause differentiation into Th2

46
Q

What class of T helper cells do neutrophils produce and how?

A

Neutrophils are recruited in response to extracellular bacteria and fungi

Release of IL-17 and 22 cause differentiation into Th17

47
Q

What is the overall sequence of the immune response?

A

Naive immune cells encounter pathogen and become activated

They produce cytokines and phagocytose pathogens

They move to lymph nodes to present antigens to specific T cells

T cells proliferate and differentiate into effector cells

CD8 cells kill pathogens and infected cells, CD4 cells activate B cells

B cells differentiate into plasma cells and produce antibodies

Phagocytes and complement cascade destroy antibody-opsonised cells

48
Q

What is the difference in serum antibody titre between first and second infections of the same antigen?

A

Secondary responses has higher antibody levels that are produced more quickly

Level after infection reduces slowly and stays higher

49
Q

What is the impact of age on the immune response?

A

Reduced thymic output thus weakened immune response

50
Q

What kind of genetic dysfunction leads to chronic granulomatous disease?

A

Loss of ROS production

51
Q

What kind of genetic dysfunction leads to Chediak-Higashi syndrome?

A

Compromised lysosomes

52
Q

What kind of genetic dysfunction is present in immunosuppression?

A

Deletion or impairment of lymphocytes

53
Q

What kind of genetic dysfunction is present in HIV?

A

CD4 T cells are destroyed

54
Q

A genetic dysfunction in the genes controlling what leads Severe Combined Immunodeficiency (SCID)?

A

Severe reduction in function of B and T cells

55
Q

What genetic disfunction leads to X-linked aggamaglobulinaemia?

A

Decreased serum IgG

56
Q

To which pathogens are Th1 made?

A

Intracellular bacteria and protozoa

57
Q

To which pathogens are Th2 made?

A

Helminths, allergens, venoms

58
Q

To which pathogens are Th17 made?

A

Extracellular bacteria and fungi

POM 4 Immunology (14 decks)

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