Chapter 17- Immunity to parasites

Question 1

Estimated that _____% of the worlds population have parasitic infections.

Answer 1

30

Question 2

Parasites are generally host specific and most of them cause chronic infections, a consequence of——————————————-?

Answer 2

Weak innate immunity and the ability of parasites to evade or resist elimination by adaptive immune responses

Question 3

Do parasites typically infect acutely or chronically?

Answer 3

chronic

Question 4

What is a benefit of their large size?

Answer 4

Lots of proteins, easy immune response

Question 5

Explain the concept of stage specific antigens?

Answer 5

antigens that are specific to the life stages of the parasite differ as the parasite matures and changes.

Question 6

What is a consequence of stage specific antigens?

Answer 6

by the time the immune system has responded to the infection the parsite expresses new antigens and is no longer a target for immune elimination.

Question 7

What type of hypersensitivity can result fro parasitic infections?

Answer 7

Type III and indirectly type IV

Question 8

Some parasites and their products induce _________ responses with concomitant fibrosis.

Answer 8

Granulomatous

Question 9

Humoral responses are most effective against ____________?

Answer 9

extracellular stages of the parasite.

Question 10

Who is responsible for Host defenses during intracellular growth?

Answer 10

Cell- mediated.

Question 11

Protozoa are usually found?

Answer 11

in the gut, in macrophages, in blood, RBCs, and muscle

Question 12

Can protozoa multiply in macrophages?

Answer 12

Yes some are reisistant to phagocytosis

Question 13

What role does IgG and C3b play in immunity to paraistes?

Answer 13

IgG and C3b deposit on parasite membrane and enhance phagocytosis (similar to opsinization)

Question 14

What is ablastin?

Answer 14

antibodies that inhibit protozoal replication by inhibiting said enzymes

Question 15

What happens to infected RBC that carry protozoa antigens on their surfaces?

Answer 15

they are opsonized and removed by splenic macrophages and or destroyed by ADCC response/

Question 16

What cells constitute the CMI response to parasites?

Answer 16

Cytotoxic T cells recognize the parasite antigens with MHC 1 and lyse the infected cells and Activated macrophages destroy intracellular parasites.

Question 17

Phagocytic cells such as neutrophils and macrophages kill helminth parasites with what?

Answer 17

toxic proteins and reactive oxygen intermediates. some have thick cuticles and are resistant to cytocidal products of neutrophils and macrophages.

Question 18

Do helminthes multiply in the host? are they intracellular or extracellular?

Answer 18

No they don’t, they are extracellular

Question 19

Major mechanism of defense against helminth parasites involve?

Answer 19

TH2 cells, IgE antibodies, eosinophils.

Question 20

Eosiniphil serum levels and IgE increase and remain high until?

Answer 20

the parasite is gone.

Question 21

Eosinophils are normally present in peripheral tissues especially?

Answer 21

mucosal linings of the respiratory, GI and Urinary tracts. They are the most abundant at sites of parasitic, allergic or inflammatory diseases.

Question 22

What level of immunity do helminth induce?

Answer 22

a low limited level.

Question 23

Growth and differentiation of eosinophils is dependent on?

Answer 23

IL-3, IL-5, GM-CSF

Question 24

why is IL-5 a significant cytokine?

Answer 24

because it also stimulates the release of eosinophils from bone marrow.

Question 25

Eosinophil membrane receptors include Fc receptors for?

Answer 25

IgG, IgA, IgE, and also complement receptors.

Question 26

the half life of eosinophils is?

Answer 26

12 days

Question 27

What are some of the granular contents of polymorphonuclear eosinophils?

Answer 27

Major basic protein
Eosinophil cationic protein
Arysulfatase B
Histaminase
Phospholipase D
Peroxidase
Colligenase
elastase
platelet activating factor

Question 28

What does the Major basic protein Do?

Answer 28

Parasite killing, neutralizes heparin

Question 29

What does Eosinophil caitionic protein do?

Answer 29

Parasite killing

Question 30

What is seen in serum as a result of parasite infection?

Answer 30

High levels of IgE and eosinophils

Question 31

How do eosinophils suppress inflammation?

Answer 31

by destroying mast cell factors.

Question 32

Activated eosiniphils produce and release?

Answer 32

lipid meadiators such as leukotrienes (LTC4,LTD4,LTE4)

Question 33

Explain how TH2 cells, mast cell, IgE and Eosinophils interact to kill parasites via ADCC

Answer 33

Stiulation of TH2 cytokines from the helminth. IL-3 and IL-4 produced stimulate mucosal mast cell growth and IL-5 stimulates the development and activation of eosinophils. Fce receptors on eosinophils mediate eosinophil binding to the IgE bound parasite.

Question 34

What proteins are found in the granules of eosinophils? what is their function?

Answer 34

Major basic protein- interacts with the negatively charged helminth membrane and is toxic to that helminth, eosinophil cationic protein= forms pores in helminth membrane.

Question 35

List at lest 3 ways in which parasites avoid immune mechanisms. Pay specific attention to stage specific immunity.

Answer 35

Shedding of glycocalyx coat, camouflaging, antigenic variation (stage specific antigens, Continuous antigenic variation) etc.

Question 36

Where are most antigens found in arthropods?

Answer 36

saliva