Immune response to pathogens Flashcards
What are the three different types of pathogen that the immune system has defences against
- Intracellular
- Extracellular
- Helminth parasites
What is immunopathology?
Immune responses to pathogens that are the capable of causing tissue injury
What are the 4 different types of PRR receptors that recognise PAMP ligands?
- Toll-like receptors – TLRs – various locations
- C-type lectin receptors – CLRs – cell surface
- RIG-I like receptors – RLRs - cytosol
- Nod-like receptors – NLRs – cytosol
What immune response occurs when TLR 7 interacts with a virus?
it activates IL-12 cytokines which causes naive T cells to become T helper cells which induce interferons
What immune response occurs when a fungus/ bacterial polysaccharide binds to the c-lectin receptor dectin-1 ?
There is expression of IL-6 and IL-23 which polarises cells to become IL-17 producing TH17 cells, this the promotes the production of neutrophils and macrophages
What is the first signal in T- Cell activation?
antigen-specific TCR engagement
what is the second signal in T cell activation?
contact with co-stimulatory ligands
What is the third signal in T cell activation?
cytokines directing T-cell differentiation into distinct effector cell
types
How do dendritic cells link the adaptive and innate immune response
they bring antigens from the site of infection and present them to T helper cells in lymph nodes which activates the T cells, allowing them to differentiate
What is the function of igA, igG, igM
virus and toxin neutralisation
What is the function of igG on macrophages
opsonisation
What is the function of igM on tumour cells?
complement fixation and formation of the membrane attack complex
What is the function of a class I interferon?
made up of interferon alpha and beta, they are secreted by virus-infected cells
What kind of infection does the MyD88 adapter protein defend against?
Invasive bacterial infections
What kind of infection does the TLR-3 protein defend against?
Herpes simplex encephalitis
What kind of infection does the Th1 pathway defend against?
“atypical” environmental mycobacteria
What kind of infection does the tH17 pathway defend against
Mucocutaneous candidiasis (fungus),
skin bacterial abscesses
How do viruses typically enter host cells
through a cell-surface receptor, the genome replication is often error-prone which leads to mutations
What is the function of a type II interferon?
modulator of adaptive immunity
What is the difference between Killer cells and Cytotoxic cells?
Killer cells are part of the innate immune response and dont need to be activated to attack cells
Cytotoxic cells are part of the adaptive immune response and attack viruses when activated by an antigen
What is the role of antibodies in the adaptive immune response?
They block infectious viruses early on in the course of infection
What are five ways viruses can evade the immune response
- Inhibition of apoptosis
- Inhibition of type 1 interferon
- production of immune modulators
- engagement of inhibitory pathways
- effection of immune cells
How does antigen drift occur?
It occurs due to the high mutation potential of the RNA genome
the RNA viruses undergo mutation and recombination which alters their genome
How does immune evasion occur in influenza A viruses?
- antigen shift occurs when different virus types try to infect a single cell
- RNA genome segments can then be swapped
- this creates new HA/ NA combinations
- a population may have little to no resistance against a new population
Name three adverse effects of anti-viral immunity
- local acute inflammation
- systemic effects of inflammation
- antibody-dependent enhancement
What is antibody-dependent enhancement?
Where an antibody actualy increases the ability of a virus to enter cells
How can antibodies work against extracellular bacteria?
- antibodies can neutralise the toxins produced by the bacteria
- antibodies can activate the complement system that mediates lysis of bacteria through the MAC
What mediates the defence against bacteria?
CHO- specific antibodies that can break down the bacterias polysaccharide capsule
how do helpter T cells assist in fighting extracellular bacteria?
they activate macrophages that enhance phagocytosis
What are some of the injurious effects of anti-bacterial immunity?
- acute inflammation can cause tissue damage
- In severe cases shock can occur, mediated by cytokines
What are leishmania?
Protozoan parasites that live in macrophage phagosomes
Usually trasnmitted by sand flies
Where do helminths typically enter the body?
through intestinal tracts
How do helminths limit immunity in the host?
decrease external aG expression or they wrap themselves in host proteins to limit immunity
What in ectoparasites triggers the immune response?
The ectoparasite blood feeding, e.g DAMPS/ Saliva etc.
Give 6 things that ectoparasite saliva can cause
- Vasodilation
- Anticoagulation/ fibrinolysis
- Complement inhibitors
- Chemokine binding
- Immunosuppresants
- Inhibition of wound healing
What mechanisms can help remove extracellular microbes?
antibodies, phagocytes, Th17
What mechanisms can help remove intracellular microbes?
antibodies, phagocytes, Th1, CTL’s
What mechanisms have evolved to help remove helminths?
igE, eosinophils, basophils, mast cells, TH2
What TLR found on viruses drives an IL-12 response that leads to the differentiation of naive CD4 T cells to become IFN-g secreting Th1 cells?
TLR7
What fungal and bacterial derived polysaccharide binds to DECTIN- 1
betaglucans
