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imin 371 > Immune response to infections > Flashcards

Immune response to infections Flashcards

1
Q

What type of responses are used to deal with viral infections?

A
  • type 2: mucosal Th2, humoral
  • type 1 cystolic: intracellular CTL and Th1
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2
Q

What type of responses are used to deal with bacterial infections?

A
  • type 2: mucosal Th2, humoral
  • type 3: extracellular Th2 and Th17
  • type 1 vesicular: intracellular Th1
  • type 1 cytosolic: CTL and Th1
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3
Q

What type of responses are used to deal with helminth infections?

A
  • type 2 mucosal: Th2, humoral
  • type 3 extracellular: Th2 and Th17
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4
Q

What type of responses are used to deal with fungi infections?

A
  • type 2 mucosal: Th2, humoral
  • type 3 extracellular: Th2 and Th17
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5
Q

What types of responses are used to deal with parasitic infections?

A
  • type 1 vesicular: Th1
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6
Q

What is the main source of damage in immune defence against bacteria, what does this imply?

A

damage is often due to host’s own immune response –> balance is needed between enough response to eliminate the pathogen and yet prevent harm to the host

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7
Q

Describe TB’s infectious replication

A
  1. enters through airway
  2. replicates in macrophages by shutting down macrophage’s ability to create lysosomes
  3. Th and mononuclear cells enter infected area
  4. formation of fibrous ring that contains the infection
    - creates tuberculous
    - damaging
  5. 90% of fibrous rings rupture –> causing active infection –> transmissible
  6. 10% of population progress to more serious disease
    - chronic pulmonary TB
    - extrapulmonary TB
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8
Q

What are triggers of activation of TB

A
  • age (ability to fight infection declines)
  • HIV infection
  • malnutrition
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9
Q

Describe two infection processes of bacteria, the host defense and bacterial evasion mechanisms

A
  1. attatchement to host cells
    - defense = blockage of attatchement by secretory IgA Abs
    - evasion = secretion of proteases that cleave IgA dimers
  2. toxin-induced damage to host cells
    - defense = neutralization of toxin by Ab
    - evasion = secretion of hyaloronidinase, which enhances bacterial invasivenss
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10
Q

Describe the immune defense against fungi

A

innate immunity controls most fungal infections:
- PRRs on innate immune cells keep fungal cells in check
- neutrophils: ROS, fungicidal substances, phagocytosis
- C albicans is a common commensal yeast, but can be a major problem in immune compromised individuals

commensal fungi crow out pathogenic fungi

Th2 is best response but excessive Th2/Treg response without Th1 –> susceptibility

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11
Q

Describe 6 immune evasion techniques used by fungi

A
  1. yeast to hyphae transition
    - escape and damage macrophages
    - prevents epithelial cells from releasing AMPs
  2. downregulation of epithelial TLR4 expression
  3. shielding of PAMP
    - hyphae have B-glucan which is detected by dectin-1
    - B-glucan is not detected when there are no hyphae
  4. complement inhibition and degradation
    - PRA1 blocks activation of C3
    - SAPs cleave complement componenets
  5. inhibition of phagolysosome formation
  6. modulation of T cell function
    - hyphae downregulate IFN-g and IL-17, and upregulate IL-10
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12
Q

Describe the differences between protozoans and helminths

A

protozoans:
- unicellular euk
- live and multiply within host cells for part of the life cycle
- usually need an intermediate host for part of life cycle and to allow transmisson to humans
- e.g. plasmodium, tyrpansome

helminths:
- adults are large and multicellular as adults
- exclusively extracellular
- enter hosts through GIT
- eggs can contaminate food, water, feces, and soil
- e.g. schistoma, pinworm, tapeworm

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13
Q

Describe the parasite trypanosoma: what illness does it cause, how is it transmitted, how does it replicate in the body, what are the symptoms, what is the immune response, how does it evade the immune response?

A
  • illness = African sleeping sickness
  • transmitted = tsetse fly bites
  • replicate = differentiates and divides every 6 hours in blood –> enters CNS
  • symptoms = microencephalitis, loss of consciousness
  • immune response = good Ab response clears most parasits
  • evasion = escape via Ag variation –> waves of parasitemia
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14
Q

Describe the immune response to helminths, and evasion strategies

A

immunity:
- don’t replicate in hosts –> limit immune engagement
- inducrtion of IgE production and recruitment of eosinophils and mast cells
- induction of Th1-mediated macrophage activation via IFN-gamma

evasion:
- decrease external Ag expression,
- wrap themselves in host proteins

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15
Q

How can helminths be used to treat disease?

A

pig whipworms:
- don’t cause us much grief
- induces Th2 response –> counterbalances proinflammaotry responses

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16
Q

Describe how viruses evade the immune system

A
  1. block MHC presentation
  2. replicate in vesicle packets to hide from innate immune response
17
Q

What are the two key viral glycoproteins of influenza? What processes are they involved in?

A
  1. HA –> attatchment to cells
  2. NA –> escape from host cells
18
Q

Where does most of the Ag variation occur for influenza?

A

HA and NA

19
Q

What are the two mechanisms of Ag variation of influenza, describe each?

A
  1. Ag drift
    - occurs due to high mutation potential of RNA genome
    - RdRp lacks proofreading
    - reason for changing flu vaccine formulation every year
  2. Ag shift
    - occurs when viruses from different species co-infect a single cell
    - RNA genome segments can be swapped in a new virus
    - can create new HA/NA combination
    - a pop may have little to no resistance against a new combination
    - responsible for pandemics
20
Q

Describe the original Ag. sin, what does this cause?

A
  • first infection causes primary response and Abs are developed against those Ags.
  • second infections (slightly different Ags) allow memory B cells to be activated and produce Abs against the original strain which are mostly effective + naive B cells that have BCRs that bind to the new Ag will be inactivated because their FcR’s will be activated by Ab’s produced by the memory cells opsonized to the virus –> no new immune response is generated
21
Q

What are the three coronaviruses that cause severe disease

A
  1. SARS-CoV-1
    - mutated out of the population
  2. MERS
    - animal resevoir = camels –> still circulating
  3. SARS-CoV-2
    - initial resevoir = horshoe bats
    - pandemic
22
Q

How is the importance of IFNs for balances anti-viral response against SARS-CoV-2 seen?

A
  • those who have a normal infection course have good IFN-1 response –> normal immune activation
  • those who have an impaired immune response –> bad initial IFN-1 response –> cytokine storm –> hyper inflammation

imin 371 (20 decks)

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