* L-12 Barriers to infection and innate antigen recognition Flashcards
What are the 4 main ways that bacteria can enter the body?
Skin breach
GI tract
respiratory tract
Genito-urinary tract
What is the main protection of the lining of the lungs and GI tract?
Mucus
How is irrigation important in preventing infection?
Constant movement of fluid such is urine through the urogenitary system acts to wash away bacteria, if it becomes blocked static urine can become infected. More examples include tears, saliva and bile.
What is the mechanism of action of mast cells?
They release inflammatory factors which increase blood flow and vascular permeability bringing components of immunity.
What is the mechanism of action of neutrophils and macrophages?
Engulf and destroy micro organisms
What is the mechanism of action of eosinophils?
Secrete factors that kill parasites like protozoa and worms
What is the mechanism of action of dendritic cells
capture antigens and present them to the adaptive immune system
What is the mechanism of action of NK cells
Destroy virus infected cells
What is the mechanism of action of the alternative complement pathway?
this is the pathway when infected by a previously unknown pathogen. It is activated by endotoxin and bacterial cell walls. It relies on soluable C3 spontaneously hydrolysing to insoluable C3b which can activate the rest of the cascade
What is the mechanism of action of acute phase proteins?
Activate classical complement pathway and opsonise. An example is C reactive protein that is produced as part of the acute phase response and initiates the classical pathway. also activate the lectin binding pathway by binding bacterial cell walls
What is the mechanism of action of cytokines (particularly interferons)
Antiviral immunity
Interferons are cytokines released by virally infected cells causing the surrounding immune cells to heighten their antiviral defences e.g. activation of NK cells
What are the three functions of dendritic cells?
- Pick up and process antigens and present them to T cells on MHC class I and II molecules
- Migrate to T cell rich areas of secondary lymphoid tissue.
- Transmit danger signals through toll receptors that help determine the right T cell responce.
Where are dendritic cells produced?
They are produced in the bone marrow before migrating to all parts of the body
What are monocytes?
Immature macrophages
What are the two families of phagocytes?
- Monocytes and macrophages
2. granulocytes - neutrophils, eosinophils and basophils
What is the difference between monocytes and mast cells?
Monocytes circulate whereas mast cells reside in tissue.
Are NK cells innate or adaptive immunity?
They do not have antigen specific receptors so are part of the innate immunity however they are lymphocytes so are sometimes considered part of adaptive - a bit of both.
What is the role of NK cells?
Mainly to do with viral immunity - kill cells that are not expressing any MHC molecules
What are pattern recognition receptors (PRRs) and what do they recognise?
They exist on innate immune cells and recognise pathogen associated molecular patterns (PAMPS)
What is the name of the main group of PRRs?
Toll-like receptors
How do toll like receptors signal when bound?
They trigger a cascade of signals within the cell that ultimately leads to activation of genes that upregulate inflammatory cytokines.
What is the complement system?
Consists of a number of soluable pro-enzymes that are found in the blood
What is the classical complement pathway?
The main pathway, activated by recognising antigen-antibody complexes. The main pathway during the adaptive immune response. Binding of a specific antibody eventually results in generation of C3 convertase. Can also be actiavted by C reactive protein that is released by the acute phase response.
What is the lectin binding pathway?
Following infection, local tissue macrophages release cytokines IL1 and IL6 which act on the liver to produce acute phase proteins. These proteins act to activate the complememt system by binding constituents of the bacterial cell walls.
