IL7 Immunity to Parasites

Question 1

Human parasites can infect

Answer 1

Arthropods (vectors)
Humans (contact, inhalation, ingestion)
Non-human primates (zoonotic spread)

Question 2

Biggest challenges posed by parasites to the immune response

Answer 2

Antigenic structure
Location over time

Question 3

Protozoan parasites

Answer 3

Least treatable tropical disease.
All unicellular and fairly motile, free-living and found in contaminated water.
Others may move from their arthropod vector hosts, such as mosquitoes and flies,m to mammalian hosts.

Question 4

Immune evasion by trypanosomes

Answer 4

Antibodies develop over time following tsetse fly bite.

Question 5

Immune modulation by helminths (metazoan)

Answer 5

• Influence activation and induce death of T cells.
• Steer the T cell response from type-1 effector pathways to type-2 effectors (progressive diesease).
• Induce polyclonal B cell activation and proliferation.
• Induce a class switch to the IgE and non-protective IgG subclasses.

Question 6

Th1 cells

Answer 6

Differentiation by IL-12
Secretes:
a) IL-2 to stimulate Th and Tc proliferation.
b) IFN-λ to activate macrophages and NK cells and IL-12.
CELL MEDIATED RESPONSE

Question 7

Th2 cells

Answer 7

Differentiation by IL-4
Secretes:
a) IL-4 to stimulate B cells to produce IgE and inhibits Th1.
b) IL-5 eosinophil growth
c) IL-10 inhibits Th1 response.
HUMORAL IMMUNITY

Question 8

Immune response generated by Schistosoma mansoni

Answer 8

IgE-mediated TH2 immunity OR Th1 IFN-λ macrophage mediated immunity.
However, the worm can cover itself with host antigens so antibodies will not see it.

Question 9

Nematodes - Ascaris lumbricoides

Answer 9

Eggs hatch in gut; larvae migrate via blood to lungs; burst out of alveoli; coughed back into gut.
500,000 eggs per day (embryonate in soil and can live for 15 years).

Question 10

Nematodes - Toxocara can is

Answer 10

Dog roundworm that can infect humans. Same lifecycle as Ascaris but cannot find lungs and causes CNS and retinal damage.

Question 11

Onchocerca volvulus

Answer 11

“River blindness” - blackfly bite, migrate into wound, microfilaria to subcutaneous tissue to form nodules below the skin.

Question 12

Enterobius vermicularis

Answer 12

Common pin worm. Infective embryonated eggs that develops in the the large intestine to migrate to anus. Not very pathogenic and eggs persis in house dust.

Question 13

Trichinella spiralis

Answer 13

Trichinosis from undercooked pork, adults live in gut but larvae move to muscle where they encyst. Inflammatory response can cause damage, other organs.

Question 14

Anisakiases
Phocanema decipiens

Answer 14

“Cod worm”, final host is seal, intermediate is fish.
Easy to see and remove.

Question 15

Anisakidae

Answer 15

Harder to spot, nearly transparent. Same host and pathology due to inflammation that leads to cancer - usually of the nile duct.

Question 16

Cestapodes (tapeworms)

Answer 16

(taenia), very large and feed on intestinal contents - mostly non-pathogenic. Shed gravid proglottids in groups (self motile).
Eggs cause cysticerci and can cause adult epilepsy if in brain.

Question 17

Trematodes

Answer 17

Infection by cercaria. Adults live in the portal tract of the liver and release eggs into the gut - significant immune pathology.

Question 18

Schistosoma mansoni immune pathology

Answer 18

Eggs sweep back into liver.
Type-2 granuloma
IL-5 and etta in
Hepatomegaly
Acute liver failure
Non-protective.

Question 19

Extracellular protozoa
Trypanosoma sp.

Answer 19

“Sleeping sickness”
Bite of tsetse fly, trypomastigotes live in blood and surface coat (VSG) changes frequently to escape immune attack.

Question 20

Extracellular protozoa
Giardia lamblia

Answer 20

Day care parasite, fecal oral transmission.
“Beaver fever”
Ingest cycsts, adults live in intestine, GI pathology.

Question 21

Extracellular protozoa
Entamoeba histolytica

Answer 21

Single celled. Erosive pathology in the gut, secondary GI infection. Serious liver involvement, occasionally CNS. Fatal untreated.

Question 22

Intracellular protozoa

Answer 22

Leishmania sp.
L. tropica - skin
L. brazilians is - mucocutaneous
L. donovan i - visceral (kala azar)

Question 23

Leishmania donovani

Answer 23

Cutaneous and visceral.
Sandfly bite, promastigotes infect macrophages, release amastigotes which can lead to pathology in the spleen and liver (kala azar). Can also uinfect skin macrophages.

Question 24

Intracellular protozoa
Plasmodium species

Answer 24

Infected by sporosoites, rapid migration to liver, leave as merozoites that infect RBCs. Massive increase, leads to anemia and decreased RBC deformability (thrombosis). Protection by heterozygous SCA.