IL7 Immunity to Parasites Flashcards
Human parasites can infect
Arthropods (vectors)
Humans (contact, inhalation, ingestion)
Non-human primates (zoonotic spread)
Biggest challenges posed by parasites to the immune response
Antigenic structure
Location over time
Protozoan parasites
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.
Immune evasion by trypanosomes
Antibodies develop over time following tsetse fly bite.
Immune modulation by helminths (metazoan)
- 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.
Th1 cells
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
Th2 cells
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
Immune response generated by Schistosoma mansoni
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.
Nematodes - Ascaris lumbricoides
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).
Nematodes - Toxocara can is
Dog roundworm that can infect humans. Same lifecycle as Ascaris but cannot find lungs and causes CNS and retinal damage.
Onchocerca volvulus
“River blindness” - blackfly bite, migrate into wound, microfilaria to subcutaneous tissue to form nodules below the skin.
Enterobius vermicularis
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.
Trichinella spiralis
Trichinosis from undercooked pork, adults live in gut but larvae move to muscle where they encyst. Inflammatory response can cause damage, other organs.
Anisakiases
Phocanema decipiens
“Cod worm”, final host is seal, intermediate is fish.
Easy to see and remove.
Anisakidae
Harder to spot, nearly transparent. Same host and pathology due to inflammation that leads to cancer - usually of the nile duct.
Cestapodes (tapeworms)
(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.
Trematodes
Infection by cercaria. Adults live in the portal tract of the liver and release eggs into the gut - significant immune pathology.
Schistosoma mansoni immune pathology
Eggs sweep back into liver.
Type-2 granuloma
IL-5 and etta in
Hepatomegaly
Acute liver failure
Non-protective.
Extracellular protozoa
Trypanosoma sp.
“Sleeping sickness”
Bite of tsetse fly, trypomastigotes live in blood and surface coat (VSG) changes frequently to escape immune attack.
Extracellular protozoa
Giardia lamblia
Day care parasite, fecal oral transmission.
“Beaver fever”
Ingest cycsts, adults live in intestine, GI pathology.
Extracellular protozoa
Entamoeba histolytica
Single celled. Erosive pathology in the gut, secondary GI infection. Serious liver involvement, occasionally CNS. Fatal untreated.
Intracellular protozoa
Leishmania sp.
L. tropica - skin
L. brazilians is - mucocutaneous
L. donovan i - visceral (kala azar)
Leishmania donovani
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.
Intracellular protozoa
Plasmodium species
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.
