EXAM #1: IMMUNOLOGY OF INFECTIOUS DISEASE

Question 1

How do extracellular bacteria evade the immune system?

Answer 1

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

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

Question 2

What is the major innate immune response against extracellular bacteria?

Answer 2

Phagocytosis via neutrophils (blood) and macrophages (tissue)

Question 3

What is the first cell to arrive in acute inflammation?

Answer 3

Neutrophils

Question 4

What do phagocytes recognize on extracellular bacteria?

Answer 4

Bacterial structure including:

1) Polysaccharides
2) Peptides (RGD sequence)

Question 5

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

Answer 5

Spleen

Question 6

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

Answer 6

Lymph nodes

Question 7

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

Answer 7

Activation of macrophages

Question 8

What metal is required for many bacteria to survive?

Answer 8

Iron

Question 9

What is MOA of lactoferrin? What cell releases lactoferrin?

Answer 9

• Neutrophils

- Lactoferrin lowers iron concentrations (starves bacteria of iron)

Question 10

What does a deficiency in C5-C9 lead to?

Answer 10

Susceptibility to N. meningitidis infection

Question 11

What is the principal immune defense against extracellular bacteria?

Answer 11

Humoral immunity i.e. antibodies

Question 12

How does humoral immunity combat extracellular bacterial infection?

Answer 12

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

Question 13

What infections are neonates susceptible to as maternal antibodies disappear?

Answer 13

• S. pneumoniae
• N. meningitidis
• H. influenzae

Question 14

What antibody can opsonize bacteria at mucosal sites?

Answer 14

IgA

Question 15

What is the most common immunodeficiency?

Answer 15

Selective IgA

*Note that IgM can compensate

Question 16

What complement pathway is specifically inhibited by a polysaccharide capsule?

Answer 16

Alternative pathway

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

Question 17

What organism drastically alters its surface adhesion proteins?

Answer 17

Neisseria

Question 18

What organisms can produce IgA1 protease?

Answer 18

1) S. pneumoniae
2) Neisseria
3) Hemophilus

Question 19

How does S. pyogenes evade immunity?

Answer 19

Interferes with complement activation via M proteins

Question 20

How does S. pneumoniae evade immunity?

Answer 20

C3 protease

Question 21

How does S. typhi evade the immune system?

Answer 21

Type III secretion system

*Prevents NFkB mediated signaling and secretion of TNF-a

Question 22

What organisms are most associated with septic shock?

Answer 22

Gram negative

Question 23

What cytokines mediate septic shock?

Answer 23

TNF-a

IL-1

Question 24

What are superantigens?

Answer 24

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

- Causes the production of TNF-a

Question 25

What causes Rheumatic Fever?

Answer 25

Cross-reactive antibodies induced by strep M-protein

Question 26

What causes poststreptococcal glomerulonephritis?

Answer 26

Antibodies form immune complexes that deposit in the kidney *Type III hypersensitivity

Question 27

What are the three major spirochetes?

Answer 27

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

Question 28

How do spirochetes enter the body?

Answer 28

Broken skin or vector *Cannot penetrate intact skin

Question 29

What is the major mechanism of immunity against spirochetes?

Answer 29

Adaptive immunity *Note a very good response from innate immunity

Question 30

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

Answer 30

Clearing infection

Question 31

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

Answer 31

Protection against reinfection

Question 32

How does T. pallidum evade the immune system?

Answer 32

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

Question 33

How does B. burgdorferi evade the immune sytem?

Answer 33

Coats self with amorphous host material

Question 34

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

Answer 34

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

Question 35

What is the major innate immune response to fungal infections?

Answer 35

Neutrophils *Note that neutropenic patients highly susceptible to C. albicans

Question 36

What is the major adaptive immune response to fungal infections?

Answer 36

Cell mediated immunity (Th1) *Can lead to granuloma formation

Question 37

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

Answer 37

IgE production (Th2)

Question 38

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

Answer 38

These organisms infect macrophages and produce a Th1 response

Question 39

What happens after macrophages are exposed to IFN-gamma?

Answer 39

1) NO production | 2) Depletion of intracellular tryptophan that is essential for some parasites

Question 40

What is the major immune mechanism against Plasmodium?

Answer 40

Th1, CTLs against intrahepatic stage

Question 41

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

Answer 41

High levels of TNFa production

Question 42

What strategies do parasites use to evade the immune system?

Answer 42

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

Question 43

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

Answer 43

Death

Question 44

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

Answer 44

- 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