Fungal and parasitic infections Flashcards
(19 cards)
What immune system is the best defence to deal with fungal infections?
The innate immune system through the use of NETs
What are NETs?
the interaction of particular receptors that lead to significant dramatic changes in neutrophils, Its DNA unwinds and becomes jelly-like. The DNA can then trap the pathogen and lysosomal enzymes attempt to break it
What ‘re the two morphological forms of fungi?
Unicellular - yeast, reproduce asexual by budding
Multicellular - Hyphae, can reproduce asexually via spores and/or sexually
Some can be dimorphic, which can switch between the two forms, such as Candida Albicans
What can other immune cells inject its DNA and trap pathogens?
Mast cells, macrophages and eosinophils
What happens in NETosis?
DNA traps the pathogen, NET-associated protease inactivates and kills the pathogen by cleaving virulence factors. The histones then disintegrate the pathogen’s cell membrane. ROS-generating enzyme carries out an oxidative attack, while antimicrobial peptides restrict the fungal growth through ion sequestration
What are fungal PAMPs?
Pathogen-Associated Molecular Patterns that are recognised by cells of the innate immune system. Fungal PAMPs include beta-glucans, mannans and chitin
What cells phagocytose conidia and single-cell fungi? What is a conidium?
Neutrophils, macrophages and dendritic cells. A conidium is a spore produced asexually from various fungi at the tip of the specialised hyphae
How can aspergillus fumigatus enter the body and what does it do?
It is a dimorphic fungus that can result in a number of unpleasant conditions such as aspergillosis, aspergilloma and swimmers ear. It is usually inhaled and can start to sprout in the lungs. If it manages to escape the immune cells it can infect the tissue and start growing
What are the side effects of NETosis?
Remnant NETs may contribute to inflammatory and chronic autoimmune disease through auto-antibodies
How does the complement act on fungi?
They cannot act via an MAC, instead through opsonisation with C3b to increase phagocytosis
How do fungi avoid detection or phagocytosis?
They can avoid detection if they contain a particular coat, either mannoprotein coat that protects them from beta-glucans or an alpha-1-3-glucan coat to cover beta-1-4-glucans, increasing their virulence. To inhibit phagocytosis, they can convert from yeast to hyphae inside the phagolysosome to burst our or if they convert extracellularly they become too big to phagocytose
What are protozoa and how are they classified?
They are unicellular and very small. They are classified based on the mode of movement, such as flagellates, ciliates, phylum sporozoa nd amoeboids
What are helminths?
Worms, they are multicellular and classified into flukes, tapeworms and roundworms
What is the difference between intracellular and extracellular protozoa?
Depending which they are depends on how the immune system will react, if extracellular (blood) it will initiate a humoral response through complement or antibodies if it is intracellular it will initiate a cell-mediated cytotoxicity response
What has caused malaria deaths and infections to fall in the past 5 years?
Vector control, insecticide in mosquito nets and indoor residual spraying as some examples
What bacteria cause malaria?
Bacteria of the plasmodium genus, P. falciparum and P. vivax being the most deadly. Others include P. ovale and P. malariae.
What is the life cycle of the malaria parasite? (long answer)
The parasite is passed through mosquitos during a bite. Enzymes present in the saliva prevents the blood from clotting, allowing the parasite to pass through easier, it then takes approximately 30 minutes to reach liver cells and infect them, they remain there until they mature into schizonts and eventually rupture the cell releasing merozoites. The merozoites will then move into the blood when there is enough and infect RBC becoming ring trophozoites, they can then go one of two ways, mature into a mature trophozoite, then into a schizont and rupturing the cell releasing more merozoites, or it can mature into a gametocyte being male or female to be taken back up by a mosquito if bitten again. In the stomach of the mosquito, the gametocytes will fuse and create a zygote, which will elongate and become motile, invading the midgut wall of the mosquito and developing into an oocyst that will grow and rupture to release sporozoites that can then move into the salivary gland completing the cycle
How long does it take from the parasite entering the body before symptoms show?
Approximately 36 hours
When are sporozoites most vulnerable?
Within the first 30 minutes of them entering the body before entering the liver, but this time-frame is too short for the immune system to act. NK cells try to limit damage to the liver and macrophages can take up infected erythrocytes in the absence of opsonising malaria-specific antibodies
