Flashcards in IIM10: Paracites, hypersensitivity and allergy Deck (92)
What is a parasite defined as?
An organism that lives in or on a host organism at the expense of this host, eukaryotic organisms that cause infections
Give three examples of parasites
unicellular protozoa or multicellular helminths or arthropods
What are protozoa?
single-celled eukaryotes that can be divided into intracellular and extracellular pathogens
What is the problem with treating protozoa infections in humans?
There is limited immunological memory of protozoal infection, but no existing vaccines. Drugs against protozoa are also toxic to the host.
What group of parasite is malaria?
What has the biggest disease burden of all parasitic infections?
Malaria: 5 species of Plasmodium
How is malaria spread? Where is it most prevalent?
The protozoa are transmitted through mosquito bites from the female Anopheles mosquitoes and is prevalent in the tropics
Where are Plasmodium falciparum and Plasmodium vivax more prevalent? (each)
Plasmodium falciparum is prevalent in Africa whilst Plasmodium vivax is prevalent in Asia and South America.
What are the three stages of a plasmodium lifecycle?
Explain the Sporozoites part of protozoa's life-cycle
Released from the Anopheles mosquito into human blood
Explain the Merozoites part of protozoa's life-cycle
Sporozoites infect liver cells, form a multinucleated mega cell known as a schizont which matures into merozoites that are released into the blood. These undergo proliferation in the RBCs and cause reinfection when RBCs rupture.
Explain the Gametocytes part of protozoa's life-cycle
Merozoites can differentiate into male and female gametocytes which are ingested by an Anopheles mosquito, where they go through the sexual phase in the stomach of the mosquito to form sporozoites.
Where can most intracellular protozoa survive?
Where do merozoites that escape the liver cells remain?
In cellular vesicles
Why can merozoites that travel in cellular vesicles, reach distant parts of the circulation?
Cellular vesicles lack immunogenic features, thus remaining undetected
How do plasmodium take advantage of the humoral response?
They have been found to proliferate better in the presence of complement and antibody
How does protozoa hiding in RBC allow them to evade detection?
RBCs lack nuclei and cannot activate transcription in response to PRR activation.
If protozoa can evade detection via RBC then how does the immune system become activated?
Rupturing RBCs act as DAMPs which activate immune responses.
In the liver stage, RNA from the parasites growing in hepatocytes can be recognised by what?
What does MDA5 activate?
MAVS-TBK1-IRF3/7 signalling that produces Type I IFNs.
In the blood stage, an APC ingests the parasites:
RNA is recognised by what?
What is parasitic DNA is recognised by in the blood stage?
What is parasitic GPI recognised by in the blood stage?
What does TLR2/1 activate after recognising parasitic GPI?
MAPK and NF-kB signalling
What does: MAPK and NF-kB signalling, MAVS-TBK1-IRF3/7 signalling and cGAS-STING-TBK1-IRF3 signalling produce?
Type I IFNs and proinflammatory cytokines
What do Schizont bursts release?
What are these sensed by?
What do they activate?
Haemozoin and uric acid which are DAMPs sensed by NLRP3 that also stimulates proinflammatory cytokine release
What type of protozoa is African sleeping sickness?
What is the name of the protozoa that cause trypanosomiasis (African sleeping sickness)?
What is trypanosomiasis transmitted by?
Tsetse fly: T. brucei travels from the bite site into the blood via the lymphatics. From the blood, it can cross into tissues and even the brain.