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Host Defense Flashcards

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1
Q

What must happen for a microbe to cause disease?

A

Must evade the host immune system

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2
Q

How long does it take for the adaptive immune system to respond to an antigen? What about if it is a memory response?

A

7 days ish

3 days if memory

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3
Q

What is the cytopathic effect of viruses?

A

Lysing of cells once virus replicates within the cell

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4
Q

What indicates a successful virus infection?

A

Entry, replication, spread, transmission

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5
Q

Why can’t microbes enter through the skin?

A

Keratinization

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6
Q

What is the role of bile in immunity?

A

Destroys lipids of enveloped viruses

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7
Q

What is the role of the nasal turbinates in immunity?

A

Impeded virus entry (narrow and complicated path)

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8
Q

True or false: there are no major physical barriers to microbe entry through the eyes and GU tract

A

True

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9
Q

What are the two hepatitis viruses that are transmitted via the fecal-oral route?

A

A and E

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10
Q

What is the major cause of the common cold?

A

Rhinoviruses and adenoviruses

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11
Q

What is the viral family of RSV?

A

Paramyxoviridae

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12
Q

What are the two major viral causes of conjunctivitis?

A

Adenoviruses

Enteroviruses

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13
Q

What is the route of transmission for the MMR viruses?

A

Respiratory

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14
Q

What are the three major components of the innate immune system?

A
  • IFN-alpha/beta
  • Natural killer cells
  • Macrophages
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15
Q

What is another name for type 2 IFN? What does this do?

A

IFN-gamma

Activates macrophages

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16
Q

What are the antiviral IFNs?

A

IFN alpha and beta

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17
Q

What are the roles of IFN alpha and beta? (4)

A
  • Prevent infection of uninfected neighboring cells
  • Increase MHC class I expression and antigen presentation
  • Activate dendritic cells and macrophages
  • Activate NK cells
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18
Q

What are the cells that produce IFN-alpha? IFN-beta?

A

IFN alpha = Leukocyte

IFN beta = Fibroblasts and other non-leukocytes

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19
Q

True or false: IFN alpha and beta have the same receptor on cells

A

True

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20
Q

What are the two pathways that IFN receptor binding can activate to inhibit protein synthesis and interrupt viral replication?

A
  • induce 2’-5’ oligoadenylate synthetase to activate RNase L to degrade mRNA
  • induce dsRNA depended protein kinase to phosphorylate eIF2 alpha and inactivate it
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21
Q

If IFN-alpha/beta activates 2’5’-oligoadenylate synthetase, what are the next two steps that lead to the inhibition of viral protein synthesis and replication?

A

Activation of RNase L, which degrades mRNA

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22
Q

If IFN-alpha/beta activates dsRNA-dependent protein kinase, what are the next two steps that lead to the inhibition of viral protein synthesis and replication?

A

eIF2-alpha is phosphorylated, inactivating it, and preventing viral protein synthesis/virus replication

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23
Q

What is the role of NK cells?

A

Lyse virus-infected cells early in viral infection

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24
Q

What activates NK cells?

A

The downregulation of MHC-class I

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25
If a virus downregulates MHC class I proteins to avoid CTLs, how can the immune system counter this?
Upregulate NK cells
26
What is the role of IFNs in NK cell activity?
Enhanced activity
27
What is the first line of defense against virus infected cells?
NK cells
28
How is it that a lack of MHC class I activates NK cells?
MHC-class I has an inhibitory effect on NK cells. Lack of inhibition will thus activate it
29
What are the cells in the body that express class I MHC?
All *nucleated* cells except corneal epithelial cells
30
What is ADCC? What cells perform this?
Antibody dependent cell-mediated cytotoxicity--cross linking of IgG Fc receptors triggers it, and induces apoptosis/perforin mediated cel death NK cells
31
Crosslinking of what type of antibody activates ADCC and NK cell killing of cells?
IgG
32
What are the two killing mechanisms that can be activated with ADCC?
Apoptosis or perforin mediated osmotic death
33
What are the antiviral effects of macrophages?
Production of TNF-alpha and NO to interfere with viral replication
34
What are the viruses that can infect macrophages? (5)
``` CMV Ebola AIDS Rubeola Rubella ``` (RACER)
35
What is the benefit to viruses if they can infect macrophages?
Facilitates viral spread
36
When in an infection is humoral immunity most important?
Early
37
What is the duration of the immunological memory at mucosal sites?
Short lived (months)
38
Where are most plasma cells locateD?
Bone marrow
39
Where do memory B cells reside? What happens when these cells encouter antigen?
Lymph nodes and the spleen Differentiate into plasma cells
40
What are the three main funtions of antibody?
Opsonization Neutralization Complement activation
41
What is the role of antibodies in the expression of viral genes?
Downregulates the expression of viral genes inside infected cells following binding of cell surface viral glycoproteins (unknown MOA)
42
How do antibodies neutralize microbes?
Prevent the microbe from binding to the host target cell
43
What is the role of CD8+ T cells?
Cell mediated destruction during an established viral infection
44
How do CD8+ T cells kill?
Perforin mediated mechanisms or apoptosis
45
What chemical do CD8+ T cells produce to enhance immunity? How does it do this?
Increase TNF-alpha | Interferes with viral replication
46
How long does it take CD8 memory cells to become activated to prevent infection?
as little as 1 day
47
What MHC protein expresses endogenous proteins?
MHC class I
48
What happens to the CD8 cells once the infection is resolved? What happens to the rest?
95% die off | Remainder become memory cells
49
What is the major difference between memory B cells, and memory T cells?
T cells are dormant | B cells continually produce low levels of Ab to ward off recurrent infection
50
What is the half-life of serum Abs?
3 weeks or less
51
How long do most plasma cells live before dying?
several days
52
What are the mechanisms for long term antibody levels?
Periodic re-exposure to a virus leading to an asymptomatic chronic infection
53
What are the viral strategies for evasion of the immune system?
Antigen alteration through point mutations or reassortment of segmented RNA genomes
54
EBV viruses can remain latent in what cells?
B cells
55
Why is the CNS an ideal location for infections?
Immunologically privileged site
56
What percent of all neonates become chronic carriers of Hep B?
90%
57
What is the role of CTLs in hepatitis B infection?
CTLs will destroy hepatocytes, leading to cirrhosis
58
What is the molecular mimicry the some viruses can undergo?
Express proteins that are similar to endogenous ones to hide themselves
59
What are the bacteria that can survive in monocytes? (3) What is the advantage of this?
Listeria, mycobacteria, Chlamydia Abs cannot get to them
60
How do macrophages attempt to rid themselves of intracellular bacteria?
Express IL-12, which activates NK cells to release IFN-gamma
61
What is the effect of IFN-gamma on macrophages?
Makes macrophages more efficient at killing intracellular bacteria, and produce NO
62
What is the effect of IL-12 on NK cells?
Encourages the release of IFN-gamma
63
True or false: some intracellular bacteria may be killed via the IFN-gamma released by NK cells, but adaptive immunity is generally required for eradication
True
64
What are the two cell types that can release IFN-gamma to macrophages to encourage the clearance in intracellular bacteria?
NK cells | Th1 cells
65
What is the result of the inability to kill mycobacteria?
Granuloma formation
66
What are the cells that mediate a granuloma formation? What are the roles of each of these?
Th1 cells and macrophages Th1 cells secrete IFN-gamma, Macrophages secrete IL-12 and wall off infection
67
What is the IL that stimulates the immune system to Th2 immunity?
IL-4
68
What is the IL that stimulates the immune system to Th1 immunity?
IL-12
69
How do granulomas impair bacterial replication? (3)
- Macrophages release NO - Fibrosis and calcification of bacteria - Decrease nutrient and oxygen supply
70
How can CTLs kill off intracellular bacteria?
If bacterial peptides are presented via MHC I, then CTLs will kill off cell
71
How do mycobacteria survive in macrophages?
Inhibit the fusion of phagosomes and lysosomes, and may scavenge ROS
72
How does listeria survive in macrophages?
Disrupts phagosome, and escapes into cytosol
73
What is tuberculoid leprosy?
TB Th1 mediated = granuloma formation + few bacteria present
74
What is lepromatous leprosy?
Th2 mediated response
75
What are the immunoglobin levels in tuberculoid leprosy? Lepromatous?
``` Tuberculoid = normal Lepromatous = hypergammaglobulinemia ```
76
What are the T cell levels in tuberculoid leprosy? Lepromatous?
``` Tuberculoid = Normal Lepromatous = low or absent ```

Infectious Disease (18 decks)

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