Parasitic immune evasion Flashcards
What are the major types of parasites?
Parasites include:
- unicellular protozoa like Rhizopoda Apicomplexa and Kinetoplastida
- multicellular helminths such as Nematoda Trematoda and Cestoda as well as arthropods like Acari and Insecta.
What is the life cycle of Toxoplasma gondii?
Toxoplasma gondii cycles between cats as definitive hosts and other vertebrates as intermediate hosts with humans infected through undercooked meat or oocysts shed by cats.
How is immunity to Toxoplasma gondii mediated?
Acute infection by tachyzoites is controlled by interferon-gamma nitric oxide and autophagy while chronic infections by bradyzoites are targeted by CD8 T cells macrophages and microglia.
What is the immune response to Entamoeba histolytica?
In the gut secretory IgA targets the Gal GalNac lectin on trophozoites providing immunity against amoebic dysentery and liver abscesses.
How does Trichinella spiralis infect hosts?
Trichinella spiralis adults reside in the small intestine while first-stage larvae encyst in muscle following the consumption of undercooked pork or horsemeat.
What is the role of basophils in immunity to ectoparasites?
Basophils play a critical role in resistance to ticks infiltrating the bite site and representing up to 70 percent of immune cells in guinea pigs.
What is immune evasion strategy 1 used by parasites?
Parasites exploit intracellular niches such as Leishmania in macrophages Plasmodium in erythrocytes and Trypanosoma cruzi in a variety of host cells to evade immunity.
What is immune evasion strategy 2 used by parasites?
Parasites like Toxoplasma gondii and Echinococcus granulosus use dormancy or slow growth with cysts that can reactivate under immunosuppression to avoid immune detection.
What is immune evasion strategy 3 used by parasites?
Parasites like Schistosomes camouflage themselves by absorbing host antigens such as MHC molecules IgG or other ligands to evade immune recognition.
What is immune evasion strategy 4 used by parasites?
Parasites such as Trypanosoma brucei change their surface proteins frequently through variable surface glycoproteins avoiding consistent immune targeting.
What is immune evasion strategy 5 used by parasites?
Parasites neutralize immune threats by inhibiting complement cascades digesting IgG or degrading chemokines like eotaxin using proteases.
What is immune evasion strategy 6 used by parasites?
Parasites like Onchocerca volvulus secrete cysteine proteinase inhibitors called cystatins that suppress antigen presentation and induce anti-inflammatory cytokine IL-10.
How do helminths influence the immune system?
Helminths drive a Th2 hyporesponsive state where Th2 cells proliferate weakly and fail to secrete IL-4 IL-5 or IL-2 but this can be reversed by blocking PD-1.
What is the role of T-regulatory cells in parasitic infections?
T-regs modulate immune responses promoting tolerance and suppressing excessive inflammation aiding in parasite survival and host-pathogen balance.
What challenges exist in developing immunity to malaria?
Malaria immunity is complicated by high parasite diversity antigenic variation and immune evasion mechanisms such as var gene expression in Plasmodium falciparum.
