Immunity to Parasites

Question 1

fuc

Answer 1

kyou

Question 2

How many pages are in the parasite section?

Answer 2

4 pages. 150-154.

Question 3

True or False. Most parasites express antigens that persist throughout their life cycle.

Answer 3

FALSE. Different antigens for different parts of the life cycle. This accounts for the difficulty in fighting certain parasites and why vaccines are difficult to create.

Question 4

True or False. Humoral response is best against intracellular parasites and Cell-Mediated response is best against extracellular parasites.

Answer 4

False. Humoral = extracellular; Cell-mediated = intracellular.

Question 5

Innate immunity of parasite defense

Answer 5

phagocytosis by macrophages and neutrophils

Question 6

adaptive immunity to parasites: Humoral

Answer 6

IgG and C3b deposited on parastie membrane enhance phagocytosis

infected RBCs with protozoan antigens on membrane are OPSONIZED and removed by macrophages or destroyed by ADCC response.

Question 7

How does a splenectomy affect immunity?

Answer 7

Latently infected animals with blood parasites may result in reactivation of the infeciton and present clinical disease again

Question 8

adaptive immunity to parasites: Cell-Mediated

Answer 8

Cytotoxic T-cells (CD8+) recognize cytosolic parastie antigens on MHC I molecules and lyse infected cells.

Activated macrophages destroy intracellular parasties

Question 9

Immunity to Helminths

Answer 9

Extracellular parasites; low level or worms results in low immunity induced/developed

phagocytic cells can kill some helminths (neutrophils and macrophages, but certainly not all

Question 10

Major mechanisms of defense against helminths

Answer 10

Th2 cells, IgE antibodies, and Eosinophils.

Question 11

What serum levels should you look at if you suspect helminth infestation?

Answer 11

IgE and Eosinophils

Question 12

What percentage of circulating leukocytes do Eosinophils constitute?

Answer 12

1-5%

Question 13

Where do eosinophils like to chill out and what do they respond too?

Answer 13

MALT and parasites, allerigies, an inflammations.

Question 14

3 cytokines for eosinophil differentiation

Answer 14

IL-3
IL-5
GM-CSF

Question 15

What is the most significant cytokine for eosinphil differntiation?

Answer 15

IL-5. it also stimulates releas of eosinophils from bone marrow…where they come from…

Question 16

Eosinophil receptors include:

Answer 16

Fc Recptors for IgG, IgA, IgE as well as complement receptors.

Question 17

What is the half-life of eosinophils in TISSUES?

Answer 17

12 days

Question 18

Granular contents of eosinophils:

Answer 18

Major Basic Protein –> parasite killing, heparin neutralizer
Eosinophil cationic protein –> parasite killing

ArylsulfataseB –> inactivates leukotrienes
Histaminase–> inactivates histamine
PhospholipaseD –> inactivates PAF
Peroxidsase & collagenase & elastase & PAF

Question 19

Can eosinophils generate a respiratory burst?

Answer 19

YES.

Question 20

True or False. Eosinophils are strong phagocytic cells.

Answer 20

FALSE. they are weak phagocytizers.

Question 21

True or False. Eosinophils are much more important for extracellular destruction of large parasites.

Answer 21

TRUE. especially since helminths are often very resistant to phagocytosis.

So, it makes sense that since our innate phagocytizers cannot handle them that our body would provide another method to defend against them.

Question 22

Do eosinophils possess proinflammatory properties even though they deactivate/suppress Mast Cell inflammatory mediators?

Answer 22

YES. eosinophils have leukotrienes which have pro-inflammatory properties.

Question 23

True or false. Prolonged inflammation is bad.

Answer 23

TRUE.

Question 24

True or false. Prolonged accumulation of eosinophils is not bad.

Answer 24

FALSE. Collagenase and Elastase can destroy/damage surrounding tissues.

Question 25

Which subset of T-Helper cells do parasites stimulate?

Answer 25

Th2 which results in production of:
IL-3
IL-4
IL-5

Question 26

What do IL-3 and IL-4 do with regards to helminths?

Answer 26

IL-3 and IL-4 stimulate mucosal Mast Cell growth.

IL-4 induces IgE isotype switching. (which eosinophils have receptors for)

Question 27

What results in rapid degranulation of Mucosal Mast Cells?

Answer 27

cross-linking of IgE by parasite antigen

Question 28

What mediates eosinophil ADCC?

Answer 28

IgG

Question 29

what receptors on eosinophils mediate IgE bound parasite?

Answer 29

Fc-epsilon receptors

Question 30

What is Major Basic Protein?

Answer 30

50% of eosinophil granules
strongly cationic–> likes negatively charged surface of parasite
it’s toxic to helminths

Question 31

What is Eosinophilic Cationic Protein?

Answer 31

Pore-forming protein that is toxic to helminths.

Question 32

What is camouflaging?

Answer 32

parasites coat themselves in HOST proteins.

Question 33

Why is antigenic variation important with regards to parasites?

Answer 33

Different antigens during different life cycles make it difficult to mount an appropriate immune response in a timely fashion.

Question 34

2 types of antigenic variation in parasites.

Answer 34

Stage-specific antigens: 
Mature parasites (adults) may express different antigens than larval stages.

Continuous antigenic variation:
Some parasites produce successive waves of progeny with different antigens.

Question 35

True or False. Some parasites express lipases which cleave Igs, removing the Fc region (effector region).

Answer 35

False. Nope, that was just to screw with your head. They secrete PROTEASES.
This makes sense since antibodies are proteins, not lipids.

Question 36

True or False. Another defense mechanism of parasites to evade host defenses is to conceal themselves in cysts.

Answer 36

True. Been to parasitology class much?

Question 37

True or False. Helminths that multiply inside macrophages employ various strategies to escape digestion by lysosomal enzymes.

Answer 37

FALSE. Protozoans do that.

Helminths are extracellular.