Lecture 5- Microbes, immunity and disease Flashcards
A virus is?
A piece of nucleic acid with a protein coat.
Some have an envelope that contains some of the host cells.
Flavivirus
RNA virus that cause a large range of diseases, often spread by mosquitoes.
Antibody
immune protein that binds to an antigen
Subclinical
infectious disease that triggers the immune system, but NO SYMPTOMS
What can cause febrile infant symptoms?
It is not always the infectious agents, but often our bodies response to them (out inflammatory pathway/immune response)
What determines recovery and why doesn’t everyone ‘catch it’
It’s our bodies individual responses/pathways that determine the length/intensity and whether we are vunerable
What of viruses can be recognised?
virus capsid particles
cells damaged by infection
virus infected cells (bits of virus end up on the viral surface)
What of bacteria/fungi can be recognised?
bacterial surface antigens
bacterial metabolites
cells damaged by infection
What does bacteria release that makes it harmful
hexotoxins
What of parasites can be recognised?
surface shapes
life cycle changes
cells damaged by infection
What allows parasites to evade the immune system?
Their constantly changing life cycle
What could be an issue is a child has had many attacks of an illness (eg- ‘cough and wheeze’)
This could indicate an ‘immunologic deficiency’
Why are children more susceptible to illness then adults>
1) Lower exposure to pathogens/bacteria so immune system has a smaller ‘memory’
2) Lack of appreciation of symptoms (slower diagnoses)
3) Not through the vaccine regime
What does a high temp and lymphadenopathy indicate?
The body is having an immune response that istriggering a physiological change.
Steps of phagocytosis
adherence membrane activation phagosome formation fusion and digestion release of degraded products
Two types of blood phagocytes?
1) Granulocytes (neutrophils- short lived)
2) blood monocytes (monocytes - longer lived)
What is the complement system?
An alternative way to stimulate inflammation & promote phagocytosis. It does this by infections (bacterial) activating a cascade of blood-derived proteins
Steps of the complement system?
1) 1st complement components (series of proteins) work together to form an ENZYME that recognises a surface antigen/shape on bacteria
2) this activates a cascade of other complement component proteins ‘complement activation cascade’
3) These activated parts help us to deal with tissue damage/infection
What are the functions of the complement system/what do the activated CC do?
1) Opsonization – enhancing phagocytosis of antigens. C3b has most important opsonizing activity (by civalently binding to surface of bacteria)
2) Chemotaxis – attracting macrophages and neutrophils (by forming chemotactic gradient)
3) Vascular permeability - Changes the blood vessel permeability, making the leakier (redness, swelling)
What of the complement system do neutrophils recognise for complement-mediated opsinisation?
C3b complement components
What do neutrophils usually recognise?
Bacterial cell wall shapes
Opsonization
Enhancing phagocytosis by coating the thing to be phagocytosed with molecules the phagocyte is able to bind to with a high affinity eg) C3b molecules
What are phagocytes of the RES (reticuloendothelial system)
different types of macrophage like cells all derived from bone marrow stem cells.
These are strategically placed in areas that they will encounter particles (alveolar macrophages of the lungs)
What is lymph?
Fluid that has leaked out of capillaries into surrounding tissue due to hydrostatic pressure. It completes its body circuit outside of the blood
