Intracellular Immunity Flashcards
What do interferons do?
Secreted within hrs of infection to protect neighbouring cells from infection by binding + blocking viral receptors
Name the Type I interferons
IFN-alpha + IFN-beta
Where are type I interferons secreted + what do they do?
- from tissue cells
- stimulate NK activity against viral cells + secretion of IFN-gamma
Name the type II interferon
IFN-gamma
Where are type II interferons secreted + what do they do?
- From activated T + NK cells
- Prevents viral growth in cells by induction of NO secretion + more intracellular IFN production
- Activates macrophages
Explain the role of Th1 in removing intracellular infections
Intracellular pathogen picked up by TCR which triggers Th1 response- activates Cd4 causing clonal expansion + production of IFNy
Explain the role of CD8 cells in intracellular immunity
Virus/ bacteria within cell can be targeted for killing by CD8: - cytotoxic granules can contain granzyme or perforin = loss of membrane integrity
- apoptosis can be triggered by CD8 cells using FasL on their surface to bind within Fas on target cell
How are macrophages involved in intracellular immunity?
Macrophages receiving activating signals from Th1 express NO + other oxygen radicals = host cell death
How do NK cells function in anti-viral immunity?
- NK cells recognise MHC I on healthy cell = doesn’t kill it
- an infected cell that doesn’t present MHC I is killed
- Viral infections often cause MHC levels to decrease
Name the 4 different types of infection
Lytic, Persistent, Latent, Transformation
Describe the differences in the effects of each type of infection
- Lytic = destruction of host cell- caused by virulent viruses
- Persistent = release viral particles slowly over long period of time
- Latent = delay b/w infection by virus + appearance of symptoms
Transformation = viruses can change a normal cell into a tumour cell
What adverse effects can be caused by viral immunity?
- inappropriate/ excessive immune responses
- causes damage to infected/ neighbouring cells
What adverse effect can be caused by distemper virus immunity?
Demyelination- brain macrophages ingest immune complexes containing distemper, release toxic products + damage neurones
What adverse effect can be caused by canine adenovirus immunity?
Blue eye- immune complexes are deposited in cornea, neutrophils respond releasing damaging enzymes = opacity to eye
Explain the differences in the role of Th1 + Th2 in fighting protozoal infections
- Abs control parasite numbers in blood + tissues = Th 2 driven
- CMI- intracellular parasites (Th1 driven)
Explain how exotoxins cause pathogenesis
secreted by bacteria- immune systems often target toxin w/ neutralising Ab but many are so toxic that they may be fatal before Ab can be produced
Explain how endotoxins cause pathogenesis
- LPS activates macrophages to release inflammatory cytokines = tissue degradation
- Lipid A = toxic if enters bloodstream- causes immune cell infiltration + activation of coagulation
What is ‘Endotoxic Shock’?
- excessive release of cytokines, often triggered by LPS
What can ‘Endotoxic Shock’ lead to?
Intravascular coagulation = defective clotting, >vascular permeability, loss of fluid into tissues,
How can bacteria cause damage to the host?
Production of superantigens to induce ineffective host immunity
What do superantigens cause?
- Hyperstimulation of immune system = overreaction, fever/ nausea/ diarrhoea/ vomiting
- Can lead to shock = organ failure, circulatory collapse
What can cause damage to infected + bystander tissues?
- overstimulation of cytokine production + complement activation by endotoxins
- Abs + CMI may damage host
- Bacterial Ags may cross-react w/ host tissue Ags = development of autoimmunity
