L10 Flashcards

1
Q

what are the evasion mechanisms done by the pathogens to avoid the immune system

A

1) Concealment of antigens

2) Antigenic variation

3) Immunosuppression

4) Interference with effector mechanisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what does Concealment of antigens mean

A

inhibition of Ag presentation by MHC 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the 2 ways for pathogen concealment of antigens

A

privileged sites

Uptake of host molecules (cloak effect)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is a privileged site

A

a site with very low immune defense

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

give examples for a pathogens that apply the concealment of antigen via privileged site

A

latency of Herpes zoster virus in CNS (chicken pox -> shingles)

hydatid cysts in Echinococcus infection (dog tapeworm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

give examples for a pathogens that apply the concealment of antigen Uptake of host molecules (cloak effect).

A

e.g. Schistosomes (bilharzia)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how is Antigenic variation achieved

A

A) large number of antigenic types

B) Mutation (antigenic drift)
e.g. ‘flu’, polio, HIV (RNA viruses)

C) Recombination (antigenic shift)
e.g. ‘flu’

D) Gene switching
e.g. trypanosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the features of Streptococcus pneumoniae

A

an example for a pathogen with big antigenic variation

Gram positive; surrounded by a thick polysaccharide capsule which protects it from phagocytosis

Antibodies to the capsule opsonise the bacteria and protect us

Large number of different capsular types (91)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how many major disease causing polysaccharide capsule does Streptococcus pneumoniae

A

23

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the vaccines for Streptococcus pneumoniae

A

Pneumovax

Prevnar 13

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the features of pneumovax

A

-polysaccharide vaccine (contains antigens to all 23 capsules)

-not effective in children under two or those with poor immune function (eg. HIV)

-low level response – just B cell IgM

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are the features of Prevnar 13

A

-conjugate vaccine.

-Only 13 capsule antigens but bound to the diphtheria toxoidwhich is highly immunogenic but non-toxic.

-T cell and B cell (all Ig) response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are the features of the Influenza virus

A

An RNA virus with a negative sense segmented genome

Can undergo antigenic drift and antigenic shift

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are the major surface antigens for the influenza virus

A

haemagglutinin

neuraminidase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what would an antigenic drift in the influenza virus result in

A

mild epidemics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what would an antigenic shifts in the influenza virus result in

A

major shifts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is an antigenic shift

A

occurs when when RNA segments are exchanged between viral strains in a secondary host

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is antigenic drift

A

mutations that alter epitopes in hemagglutinin so that neutralizing antibodies no longer bind

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is an example for gene switching

A

Trypanosoma brucei

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what are the features of Trypanosoma brucei

A

-Protozoal parasite that causes African sleeping sickness

-Spread by the Tsetse fly

-Patients undergo bouts of parasitaemia

-Correlates with changes in the major surface antigen of the trypanosome, brought about by genetic rearrangement

-Variant-specific glycoprotein (VSG)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is Variant-specific glycoprotein (VSG)

A

the area that gets genetically recombined in Trypanosoma brucei

22
Q

how many VSG genes are expressed at one time

23
Q

how is immunosuppression achieved

A

1- infection of immune cells

2- Induction of regulatory T cells

24
Q

give an example for pathogens that cause infection of immune cells

A

HIV -T cells (CD4+) /macrophage/dendritic cells

25
Q

give an example for pathogens that cause Induction of regulatory T cells

A

chronic infection with Helicobacter pylori

leishmania

measles virus

26
Q

what are the features of Helicobacter pylori

A

Gram negative bacterium that causes gastric and duodenal ulcers (also gastric adenocarcinomas)

Found in about one in three people, but causes disease in only about 10% of people who are infected

Regulatory T cells may be involved in allowing it to establish a persistent infection

27
Q

what markers do T reg cells express

A

CD4 and CD25

28
Q

what are the features of leishmania

A

Parasite - genus of trypanosomes

Vector – sand fly

Can hide and survive in macrophages

Can increase expression of TREG cells

Decrease immune response

29
Q

what are the features of measles virus

A

An RNA virus; disease is associated with a rash commonly accompanied by profound malaise and respiratory symptoms

Complications include secondary bacterial respiratory infections

Causes immunosuppression which can lead to secondary infections

Shown to infect dendritic cells

Infected dendritic cells show
- increased apoptosis
- decreased stimulation of T cells
- decreased IL-12 production (NK cells and TH1 affected)

30
Q

what effector mechanisms are affected in the evasion of immune defenses

A

A) Molecules interfering with antibody function

B) Molecules interfering with complement

C) Molecules binding cytokines

D) Subvert responses by producing molecules with cytokine activity

31
Q

give examples for Molecules interfering with antibody function

A

e.g IgA proteases (Streptococcus pneumoniae, Neisseria spp.)

Fc-binding molecules (Staphylococcal protein A; Herpes simplex virus)

32
Q

give examples for molecules interfering with compliment

A

Enzymes that break down C3a/C5a (Pseudomonas)

Molecules that inhibit complement activation (Vaccinia/smallpox virus)

33
Q

give an example for a molecule interfereing with cytokines and what pathogen makes it

A

IFN - gamma, small pox

34
Q

give an example of subvert responses by producing molecules with cytokine activity

A

epstein barr virus - vIL-10 (downregulates Th1 response)

35
Q

How can TB inhibit phagocytic lysis?

A

Inhibiting fusion with the phagosomes

36
Q

What is immunopathology?

A

An infectious disease pathology that may result from direct effects of a pathogen or host responses

37
Q

What are the pathalogical consequences of immune responses and how can it be induced by a pathogen

A

LPS = induces Mq cytokine secretion (Il1 TNF alpha via TLR 4) = fever, endotoxic shock, cytokine storm.

38
Q

What is the role of TNF alpha

A

Acvtivates vascular endotheliuim and increases vascular permeasibility - leads to increased entry of IgG, complement & cells to tissues and increased fluid drainage to lymph nodes = fever mobilisation of metabolites shock

39
Q

What happens during sepsis?

A

Systemic infection, mass cytokine release = multiple organ failure = death

40
Q

Can Ab/T cell reactions contirbute to pathology? Provide an example

A

Yes, skin rashes in measles due to T cells & granula formation in TB due to chronic Mq activation

41
Q

Can microbes play a role in initiating autoimmune responses - provide an example

A

Yes. Ab to certain proteins can cross-react with heart muscle

42
Q

What’s the fatality rate for ebola?

43
Q

What is ebola?

A

folivirus: enveloped, non-segmented negative stranded RNA with filamentous particles

44
Q

What can ebola cause?

A

haemorrhagic fever

45
Q

Where is the largest outbreak of ebola in history?

A

West Africa

46
Q

What cells of the immune defence does ebola impact?

A

dendritic and mq

47
Q

What impact can ebola have on cells?

A

inhibits maturation of infected dendritic cells = ineffective Ag presentation

48
Q

What does ebola lead to?

A

Apoptosis = reduced numbers of T lymph. and NK cells & weakened immune responses

49
Q

Does ebola interfere with the production of IFN Type 1?

A

Yes, and cellular response to IFN as well

50
Q

How does ebola contribute to immunopathogenesis via infection of Mq?

A

induction of cytokine storm (glycoprotein from virus binds to Mq & dendritic cells = cytokine release = increased vascular permeability)

infected Mq express abundant tissue factor = coagulation cascade - disseminated IV coagulation = death