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Infectious Disease > EXAM #1: IMMUNOLOGY OF INFECTIOUS DISEASE > Flashcards

EXAM #1: IMMUNOLOGY OF INFECTIOUS DISEASE Flashcards

1
Q

How do extracellular bacteria evade the immune system?

A

1) Induction of vigorous inflammation
2) Production of toxins that kill host cells

*So we try to kill the bacteria and neutralize the toxins

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2
Q

What is the major innate immune response against extracellular bacteria?

A

Phagocytosis via neutrophils (blood) and macrophages (tissue)

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3
Q

What is the first cell to arrive in acute inflammation?

A

Neutrophils

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4
Q

What do phagocytes recognize on extracellular bacteria?

A

Bacterial structure including:

1) Polysaccharides
2) Peptides (RGD sequence)

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5
Q

What is the main immunologic responder to blood-born pathogens?

A

Spleen

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6
Q

What is the main immunologic responder to tissue-born pathogens?

A

Lymph nodes

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7
Q

What is the role of unmethylated CpG dinucleotide motifs in the immune system?

A

Activation of macrophages

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8
Q

What metal is required for many bacteria to survive?

A

Iron

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9
Q

What is MOA of lactoferrin? What cell releases lactoferrin?

A
  • Neutrophils

- Lactoferrin lowers iron concentrations (starves bacteria of iron)

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10
Q

What does a deficiency in C5-C9 lead to?

A

Susceptibility to N. meningitidis infection

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11
Q

What is the principal immune defense against extracellular bacteria?

A

Humoral immunity i.e. antibodies

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12
Q

How does humoral immunity combat extracellular bacterial infection?

A

1) IgG opsonization
2) Toxin-specific antibody neutralization
3) IgM and IgG activate classical complement pathway

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13
Q

What infections are neonates susceptible to as maternal antibodies disappear?

A
  • S. pneumoniae
  • N. meningitidis
  • H. influenzae
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14
Q

What antibody can opsonize bacteria at mucosal sites?

A

IgA

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15
Q

What is the most common immunodeficiency?

A

Selective IgA

*Note that IgM can compensate

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16
Q

What complement pathway is specifically inhibited by a polysaccharide capsule?

A

Alternative pathway

*Note that IgG and C3b can bind and opsonize these bacteria for elimination

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17
Q

What organism drastically alters its surface adhesion proteins?

A

Neisseria

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18
Q

What organisms can produce IgA1 protease?

A

1) S. pneumoniae
2) Neisseria
3) Hemophilus

19
Q

How does S. pyogenes evade immunity?

A

Interferes with complement activation via M proteins

20
Q

How does S. pneumoniae evade immunity?

A

C3 protease

21
Q

How does S. typhi evade the immune system?

A

Type III secretion system

*Prevents NFkB mediated signaling and secretion of TNF-a

22
Q

What organisms are most associated with septic shock?

A

Gram negative

23
Q

What cytokines mediate septic shock?

A

TNF-a

IL-1

24
Q

What are superantigens?

A
  • Toxin that binds Class II MHC on APCs and T-cells

- Causes the production of TNF-a

25
Q

What causes Rheumatic Fever?

A

Cross-reactive antibodies induced by strep M-protein

26
Q

What causes poststreptococcal glomerulonephritis?

A

Antibodies form immune complexes that deposit in the kidney

*Type III hypersensitivity

27
Q

What are the three major spirochetes?

A

1) Treponema pallidum (Syphillis)
2) Borrelia burgdorferi (Lyme)
3) Leptospira

28
Q

How do spirochetes enter the body?

A

Broken skin or vector

*Cannot penetrate intact skin

29
Q

What is the major mechanism of immunity against spirochetes?

A

Adaptive immunity

*Note a very good response from innate immunity

30
Q

What is the role of cell-mediated immunity (Th1) in spirochete infection?

A

Clearing infection

31
Q

What is the role of humoral (Th2) immunity in spirochete infection?

A

Protection against reinfection

32
Q

How does T. pallidum evade the immune system?

A

Lacks virulence factors ; is simply very resistant to normal host mechanisms

33
Q

How does B. burgdorferi evade the immune sytem?

A

Coats self with amorphous host material

34
Q

What are the manifestations of an overzealous immune response against spirochetes?

A

1) Rash of secondary syphilis is Type III hypersensitivity reaction
2) Lyme arthritis is caused by T-cells

35
Q

What is the major innate immune response to fungal infections?

A

Neutrophils

*Note that neutropenic patients highly susceptible to C. albicans

36
Q

What is the major adaptive immune response to fungal infections?

A

Cell mediated immunity (Th1)

*Can lead to granuloma formation

37
Q

What is the major immune response to helminth/worm infections?

A

IgE production (Th2)

38
Q

What are the major adaptive immune responses to protozoa (Leshmania and Trypanosoma)?

A

These organisms infect macrophages and produce a Th1 response

39
Q

What happens after macrophages are exposed to IFN-gamma?

A

1) NO production

2) Depletion of intracellular tryptophan that is essential for some parasites

40
Q

What is the major immune mechanism against Plasmodium?

A

Th1, CTLs against intrahepatic stage

41
Q

What is the major deletarious effect of the immune response to Plasmodium?

A

High levels of TNFa production

42
Q

What strategies do parasites use to evade the immune system?

A

1) Conceal in intestinal lumen
2) Coat with host proteins
3) Inhibition of complement activation
4) Production of enzymes that cleave membrane bound antibodies

43
Q

What is a high level of TNF-a production in childhood malaria infections prognostic for?

A

Death

44
Q

What do you need to remember about vaccines and parasite infected areas?

A
  • Vaccines= Th1 immune response
  • Chronic parasite infestation can induce strong Th2 response

*Thus, b/c of the reciprocal relationship between these two immune reactions, vaccines may not be as efficacious

Infectious Disease (21 decks)

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