EXAM #1: IMMUNOLOGY OF INFECTIOUS DISEASE Flashcards by Jonathan Kallevang

How do extracellular bacteria evade the immune system?

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

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

How well did you know this?

Not at all

Perfectly

What is the major innate immune response against extracellular bacteria?

Phagocytosis via neutrophils (blood) and macrophages (tissue)

How well did you know this?

Not at all

Perfectly

What is the first cell to arrive in acute inflammation?

Neutrophils

How well did you know this?

Not at all

Perfectly

What do phagocytes recognize on extracellular bacteria?

Bacterial structure including:

1) Polysaccharides
2) Peptides (RGD sequence)

How well did you know this?

Not at all

Perfectly

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

Spleen

How well did you know this?

Not at all

Perfectly

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

Lymph nodes

How well did you know this?

Not at all

Perfectly

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

Activation of macrophages

How well did you know this?

Not at all

Perfectly

What metal is required for many bacteria to survive?

Iron

How well did you know this?

Not at all

Perfectly

What is MOA of lactoferrin? What cell releases lactoferrin?

Neutrophils

- Lactoferrin lowers iron concentrations (starves bacteria of iron)

How well did you know this?

Not at all

Perfectly

What does a deficiency in C5-C9 lead to?

Susceptibility to N. meningitidis infection

How well did you know this?

Not at all

Perfectly

What is the principal immune defense against extracellular bacteria?

Humoral immunity i.e. antibodies

How well did you know this?

Not at all

Perfectly

How does humoral immunity combat extracellular bacterial infection?

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

How well did you know this?

Not at all

Perfectly

What infections are neonates susceptible to as maternal antibodies disappear?

S. pneumoniae
N. meningitidis
H. influenzae

How well did you know this?

Not at all

Perfectly

What antibody can opsonize bacteria at mucosal sites?

IgA

How well did you know this?

Not at all

Perfectly

What is the most common immunodeficiency?

Selective IgA

*Note that IgM can compensate

How well did you know this?

Not at all

Perfectly

What complement pathway is specifically inhibited by a polysaccharide capsule?

Alternative pathway

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

How well did you know this?

Not at all

Perfectly

What organism drastically alters its surface adhesion proteins?

Neisseria

How well did you know this?

Not at all

Perfectly

What organisms can produce IgA1 protease?

1) S. pneumoniae
2) Neisseria
3) Hemophilus

How does S. pyogenes evade immunity?

Interferes with complement activation via M proteins

How does S. pneumoniae evade immunity?

C3 protease

How does S. typhi evade the immune system?

Type III secretion system

*Prevents NFkB mediated signaling and secretion of TNF-a

What organisms are most associated with septic shock?

Gram negative

What cytokines mediate septic shock?

TNF-a

IL-1

What are superantigens?

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

- Causes the production of TNF-a

What causes Rheumatic Fever?

Cross-reactive antibodies induced by strep M-protein

What causes poststreptococcal glomerulonephritis?

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

What are the three major spirochetes?

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

How do spirochetes enter the body?

Broken skin or vector *Cannot penetrate intact skin

What is the major mechanism of immunity against spirochetes?

Adaptive immunity *Note a very good response from innate immunity

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

Clearing infection

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

Protection against reinfection

How does T. pallidum evade the immune system?

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

How does B. burgdorferi evade the immune sytem?

Coats self with amorphous host material

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

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

What is the major innate immune response to fungal infections?

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

What is the major adaptive immune response to fungal infections?

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

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

IgE production (Th2)

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

These organisms infect macrophages and produce a Th1 response

What happens after macrophages are exposed to IFN-gamma?

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

What is the major immune mechanism against Plasmodium?

Th1, CTLs against intrahepatic stage

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

High levels of TNFa production

What strategies do parasites use to evade the immune system?

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

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

Death

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

- 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