Immune system Flashcards
What is the immune system?
It recognises and responds to non-self entities in the body
Name some non-self entities that the immune system targets
Viruses, Bacteria, Parasites, malignancies and grafts
Name some functions that the immune system has to undertake?
- detect and identify non-self
- Communicate with other cells
- recruit
- destroy or suppress
What are the 2 types of immune tissues?
- Primary lymphoid tissues
- secondary lymphoid tissues
When is something considered a primary lymphoid tissue?
When it produces white blood cells
Name 2 structures in the primary lymphoid tissue?
- Thymus
- bone marrow
Name two structures in the secondary lymphoid tissues?
- Spleen
- lymph nodes
What else occurs in tissues?
Aggregations of immune cells also occur in other tissues (i.e. the gut)
Compare Innate and adaptive immunity
Activation of the innate immunity can increase what?
The memory responses of the adaptive system, increasing its effectiveness
Tell me the relative activity of cells in the body when a infection arises
Name some ways that pathogens can invade the body?
- Cuts/wounds/post-operation e.g. Staph. aureus
- Insect bites- (e.g. sand-fly-leishmania, mosquito –malaria)
- Animal bites ––environmental pathogens and rabies
- Airborne e.g. Mycobacterium tuberculosis
- Food E. coli & Salmonella
- Human behaviour IV drug user’s HIV and hepatitis
In early experiments, 1845-1916, what did the scientist Metchnikoff show?
What did he incorrectly suggest?
- He showed that cells (white blood cells) termed phagocytes could ingest microbes- these were more active from vaccinated animals
- Metchnikoff (incorrectly) suggested that cells rather than serum components were the major effectors of immunity.
- Phagocytes were later identified as monocytes/macrophages and neutrophils as the major effector cells
Name some defence mechanisms of the innate response to a virus
- mucus
- antigen presenting cells
- phagocytes
- cytokines
- neutrophils
- lymphocytes
Name some non-specific defences and how they work/ what they produce?
Whats inflammation, name some things that can cause it
Inflammation is a complex biological response of the body tissues to harmful sitmuli such as…
- pathogens
- damaged cells/ tissues
- irritants
Tell me the steps to how inflammation allows the immune system access to damaged/ infected tissues in order to remove necrotic cells and tissues to intiate repair?
- bacteria trigger macrophage to release cytokines and chemokines
- vasodilation and increased vascular permeability cause redness, heat and swelling
- inflammatory cells migrate into tissues releasing inflammatory mediators that cause pain
Whats vasodilation?
What physical effects does it cause?
There is an increase in diameter of adjoining capillaries constriction of vessles transporting blood away
physical effects:
- redness
- swelling
- heat
When theres inflammation, what do resident macrophages and damaged tissue cells release?
chemical signals and alter endothelia cells
Name 3 processes that occur when inflammation is present?
- Margination
- Extravasation
- Chemotaxis
Whats margination?
Inflammation attracts monocytes and neutrophils- rolling (adherence) to endothelial of venules
Whats Extravasation?
Emigration from vessel between the endothelial cells into the tissue
Whats Chemotaxis ?
Migrate to the site of injury/ invasion
During the margination of neutrophils, what generally occurs?
The RBC clump together to make space for neutrophils in the vessel
Whats meant by neutrophil nets ?
When neutrophils shoot out DNA/chromatin and coat bacteria
Name the cells of the immune system
Their classification
Their primary function(s)
Where are monocytes found?
What happens when they are activated in tissues?
Monocytes are found in the blood, when they are activated in tissues they differentiate into macrophages
Where may macrophages reside?
They may reside for a long time in the same tissue
Whats the role of macrophages?
To remove pathogens and dead or dying cells by phagocytosis
(neutrophils and eosinophils are also phagocytes)
Explain the process of phagocytosis
When is pathogen killing initiated?
Whats released?
Once the phagocytic vacuole fuses with a lysosome forming a phagolysosome with release of:
- oxygen radicals
- chlorine products
- Nitric oxide pathway
What is NADPH oxidase?
Where is it located during phagocytosis?
NADPH oxidase is a membrane-bound enzyme complex
It faces the inner space of phagosomes
During phagocytosing, what does the cell undergo?
A massive increase in metabolism
What does the respiratory burst produce?
Reactive oxygen species (ROS)
What reaction does NADPH oxidase catalyse?
When Superoxide, O2- is produced, what reactions can occurs, (with enzymes), to produce toxic products?
What can these products destroy?
Superoxide, Hydrogen Peroxide, Chlorine, Hypochlorite and Hydroxyl radical, all extremely toxic
destroying lipid membrane and bacterial DNA (kept in vesicles to help protect the cell)
What kind of receptors can the innate immune system use and what are these?
The innate immune system uses receptors that can detect the repeating patterns in the surface of microorganisms
Name some pattern recognition receptors
Where do they bind/ recognise?
- mannose receptor binds mannose residues on pathogen surface
- glycan receptor binds to polysaccharides of bacteria and yeast
- scavenger receptor recognises complex sugars on yeast and bacteria
- TLR (Toll-like receptor) binds to LPS (lipopolysaccharide) on the cell wall of gram-negative bacteria
- Complement receptor (CR) recognises complement covered structures on yeast and bacteria
What are toll like receptors?
Transmembrane receptors that signal to immune cells the type of pathogen that has invaded
Name the Toll like receptors
What are each of their ligands?
Whats their source?
Provide an example for each?
Here is an example of LPS and TLR4
What are interferons?
cytokines that inhibit viral replication within cells
What do activated macrophages release and what does this stimulate?
Activated macrophages release IL-12
This stimulates IFNγ by natural killer cells
What does IFNγ lead to?
further macrophage activation in a feedback loop amplifying innate immune responses- increasing phagocytosis and iNOS expression
What do the interleukins IL-1 and TNFα induce?
endothelial cells to express adhesion molecules allowing neutrophils and monocytes to bind and leave the bloodstream
What is IL-8?
A potent neutrophil chemoattractant and activates macrophages
What do TNFα, PAF and PG act directly on?
endothelium to increase permeability
What does PAF cause?
platelets to release histamine also increases vascular endothelial permeability
