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Host Defense > Immunity to Infection > Flashcards

Immunity to Infection Flashcards

1
Q

What are the 4 classes of microorganisms that cause disease in humans?

A
  • extracellular pathogens (gram + and - bacteria, parasites, fungi)
  • intracellular pathogens (bacteria, parasites)
  • viruses (intracellular)
  • parasitic worms (extracellular)
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2
Q

What are common routes of infection for pathogens?

A
  • mucosal surfaces (mouth, respiratory tract, GI tract, reproductive tract)
  • opportunistic pathogens
  • external epithelia (external surfaces, wounds/abrasions, insect bites)
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3
Q

Which class of microorganisms are opportunistic pathogens?

A

mainly fungi (esp. associated w/ opportunistic infection in the immunocompromised)

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4
Q

Intracellular bacteria mainly cause disease where?

A

in the GI tract

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5
Q

List the physical barriers to infection and how they mediate protection.

A
  • skin (thick, multilayered, low moisture)

- mucosal surfaces (mucus secretion, ciliated epithelium, secretory IgA)

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6
Q

List the chemical barriers to infection and how they mediate infection.

A
  • lysozyme (enzyme present in saliva and tears, specific for bacteria)
  • antimicrobial peptides (released by a range of cells, form pores in pathogen surface that ultimately lead to death of pathogen, ex. include defensins, cathelicidins, and histatins)
  • acidity (pH) of skin
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7
Q

Which type of chemical barrier (specifically, antimicrobial peptide) mediates destruction of a type of extracellular pathogenic fungus?

A

histatins

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8
Q

What is a primary site of infection in the human body?

A

mucosal surfaces (even more so than skin)

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9
Q

Which types of pathogens can infect mucosal surfaces?

A

fungi, bacteria, viruses, and parasites (non-discriminatory)

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10
Q

Is lysozyme specific or non-discriminatory?

A

It is specific to bacteria (mostly gram positive, some gram negative, NO others!)

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11
Q

What is the specificity of defensins and cathelicidins?

A

broad-acting (can act on bacterial, fungal, viral)

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12
Q

Disease only progresses upon what?

A

breach of physical AND chemical barriers

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13
Q

Which type of mutation (w/ regard to PAMP sensors) is implicated in Crohn’s disease?

A

NOD-2; mutations linked to intestinal impermeability and inflammation due to improper recognition of bacterial byproducts and dysbiosis

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14
Q

What is the difference between Toll-like and NOD-like receptors?

A

Toll-like receptors recognize extracellular bacteria and viral pathogens; NOD-like receptors recognize intracellular bacteria

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15
Q

What does TLR2 recognize?

A

lipoteichoic acid (on gram pos. bacteria) and lipoproteins (on gram pos. and gram neg. bacteria)

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16
Q

What does TLR4 recognize?

A

lipopolysaccharide (LPS) on gram neg. bacteria

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17
Q

What does TLR3 recognize?

A

ds-RNA (viruses)

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18
Q

What does TLR5 recognize?

A

flagellin (bacterial motility component)

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19
Q

What does TLR7/8 recognize?

A

ss-RNA (viruses)

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20
Q

What does TLR9 recognize?

A

bacterial/viral DNA (bacteria AND herpes virus)

21
Q

What does NOD1 recognize?

A

peptidoglycan of gram neg. intracellular bacteria (ex: Salmonella)

22
Q

What does NOD2 recognize?

A

peptidoglycan of gram pos/neg intracellular bacteria, PLUS Mycobacterium tuberculosis

23
Q

NOD2 receptors are found highly enriched within cells of _______.

A

the gut

24
Q

What are specific examples of the bacteria recognized by NOD-like receptors?

A

Salmonella, Listeria, M. tb

25
Q

Which TLRs are the viral TLRs?

A

TLR3, TLR7/8, TLR9

26
Q

Which TLRs are located within endosomal compartments of host cells?

A

viral TLRs

27
Q

What is the role of NOD2 in host homeostasis?

A

It maintains intestinal homeostasis and healthy microbiota.

28
Q

Can fungi use the same recognition receptors as bacteria and viruses? Explain.

A

No, as the composition of the fungal cell wall is entirely different. The glucan receptor is needed to recognize the β-glucans that comprise the fungal cell wall. (ex: acapsular Cryptococcus neoformans)

29
Q

Is respiratory (oxidative) burst universal or specific to a particular pathogen?

A

It is a universal pathogen killing mechanism.

30
Q

What is an example of an infection caused by defects in oxidative burst?

A

Chronic Granulomatous Disease

31
Q

What is NADPH oxidase involved with?

A

It is a complex that delivers antimicrobial proteases into the phagolysosome.

32
Q

Which antimicrobial is the key to killing pathogens?

A

superoxide

33
Q

What are key infectious microorganisms associated with Chronic Granulomatous Disease?

A

staph. aureus and other catalase-positive bacteria

34
Q

Type I interferons are associated with _________ immune functions.

A

anti-viral

35
Q

What are the 2 classic Type I interferons?

A

IFNα and IFNβ

36
Q

What is the mechanism of action of the Type I interferons?

A

They act on cells surrounding the virally-infected cell and induce Interferon Stimulated Genes (ISGs) that prevent viral synthesis and contain viral spread.

37
Q

How do NK cells work to rid the body of viral infection?

A

They release cytolytic granules that can induce cellular apoptosis. (key point is that they kill the CELL so it cannot propagate – do NOT kill the virus itself)

38
Q

Is the MAC a mechanism by which fungal infections are cleared?

A

No, as fungi are highly resistant to the MAC. However, they ARE efficiently opsonized by C3 to promote phagocytosis.

39
Q

Opsonization is specific to which types of pathogens?

A

extracellular bacteria and fungi (which are also extracellular) - ex: Staph. aureus, Vibrio cholera, Strep. pyogenes, Strep. pneumoniae

40
Q

Toxin neutralization is specific to which types of pathogens?

A

bacterial pathogens (NOT viruses) - ex: cholera toxin of Vibrio cholerae bacteria can be neutralized by toxin-specific IgA in the gut

41
Q

Cell lysis by MAC is specific to which types of pathogens?

A

gram (-) bacteria and NOT gram (+) bacteria (fungi are also particularly resistant to MAC)

42
Q

Opsonization with C3 (and recog. by C3 receptor) is specific to which types of pathogens?

A

gram (+) or (-) bacteria, as well as most other foreign pathogens (broad and generalizable)

43
Q

Which gram (-) bacteria is particularly sensitive to the MAC?

A

Neisseria meningiditis

44
Q

Why do many fungi and parasites (specifically, parasitic worms) have difficulties being phagocytosed?

A

Many are larger than the immune cell trying to engulf it. An alternate mechanism INDEPENDENT of complement system is therefore needed, like Ab-dependent cellular cytotoxicity (ADCC).

45
Q

What are examples of induction of adaptive immunity to help clear a pathogen?

A

-neutralization by antibodies
-opsonization by antibodies
-complement activation by antibodies
(specific antibodies directed against all pathogens=crucial for effective protective immunity)

46
Q

Give an example of antibody-dependent cellular cytotoxicity (ADCC).

A

IgE antibodies bind to the surface of a parasitic worm, recruiting eosinophils that recognize the Fc receptor of the IgE antibodies. The eosinophils then know that a parasite is present and will degranulate to kill the helminth.

47
Q

The Th1 response is involved with clearance of which class of pathogen?

A

intracellular bacteria (ex: M. tb and Listeria)

48
Q

Mycobacterium tuberculosis is very good at preventing which type of immune response?

A

Th1 response

49
Q

Clearance of viral infection is highly dependent on the induction of…

A

cytotoxic CD8+ T-cells in conjunction w/ Ab and NK cell-mediated responses

Host Defense (24 decks)

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