Innate immunity Flashcards
Why do we need an immune response?
Prevent infections and cancers
Remove dead/non-functioning components
Physical barriers
Skin Cilia Hairs Mucus Flushing action of tears/urine
Characteristics of viruses
Obligate intracellular pathogen
20-800 nm
Characteristics of bacteria
Prokaryote
0.2-20 micrometers
Characteristics of fungi
Eukaryote
2 micrometers to a centimetre
Characteristics of a protozoal parasite
Two or more hosts
10-200 micrometers
Characteristics of multicellular parasites
Multiple lifestyles
1 cm to 3 m
What is desquamination?
Constant turnover of skin cells
What do goblet cells do?
Produce mucus
Which cells are part of gastric immunity?
Goblet and dendritic cells
Chemical defences of the body
Lysozymes
Normal flora
Stomach acid
Why is normal flora beneficial?
Gets rid of pathogens and stops them binding
What is the order of defence in the body?
1st line - physical barriers
2nd line - innate immune system
3rd line - adaptive immune system
What do all cells in the innate immune system start as?
Pluripotent stem cell
Which cell do most defence cells come from?
Myeloid progenitor
What do granulocytes do?
Degranulate contents to fight pathogens
What do neutrophils do?
Phagocytosis
What do basophils do?
Granulocyte, similar to neutrophil
What do monocytes do?
In tissue, they differentiate into macrophages
What do megakaryocytes do?
Produce platelets/phagocytose/present antigensW
What do mast cells do?
Initiate inflammatory immune response
What do dendritic cells do?
Present antigens
Where do cells in the adaptive immune system come from?
Lymphoid progenitor
Characteristics of mast cells
Granulocyte
Large nucleus
Signals from DAMP/PAMP
Releases granules
What do the granules released from mast cells do?
Recruit immune cells
Regulates phagocytosis
Repairs tissues
Vascular permeability
What impact do mast cells have on vasculature during inflammation?
Cause vasodilation in smooth muscle cells
Makes blood vessels leaky and swell
Endothelial cells have adhesion molecules activated by mast cells and they get sticky. This is where WBCs bind to enter tissue
Plasma proteins leak into tissue to fight infection
Symptoms of inflammation
Rubor/calor
Dolor
Swelling
What do dendritic cells do?
Pick up pathogens in tissue and travel to lymph node
Present pathogen to immature T-cells to activate them
Activates T-cells and coordinates correct immune response
How are T-cells drawn to the site of an infection?
Cytokines
What is chemotaxis?
Movement along gradient of increasing concentration of the attractant
How many nuclei do neutrophils have?
Multiple
What do neutrophils do?
Phagocytose pathogens
Respiratory burst
How are leukocytes recruited to an area?
Follow chemotactic gradient
Adhesion molecules are activated and become sticky
Receptors bind to adhesion molecules
Slow down leukocyte until bound to endothelial cells
Gaps in tight junctions allow neutrophils to enter tissues
How does phagocytosis occur?
Immune cell attaches to pathogen by recognition receptors
Pseudopodia wraps around pathogen
Neutrophil degranulates
What is a respiratory burst?
Free radicals produced to break down pathogens
E.g. after opsonin/ligand binding to cell surface receptors, the NADPH oxidase generates superoxide (O2.) in phagocytes. Superoxide dissimulates into H2O2, which reacts with chloride ions to form hypochlorous acid (HOCl) catalyzed by myeloperoxidase
Which cells can present antigens?
Macrophages
Dendritic cells
B-cells
What do macrophages do?
Phagocytosis
Respiratory burst
Present antigens and take to lymph nodes to inform about infection
Where do NK cells come from?
Lymphoid
Why are NK cells classified as innate?
They don’t need to be activated
How do NK cells kill pathogens?
They have ‘death-receptors’ on membrane which bind to ‘death receptor’ ligands on pathogen. When bound, Nk cell degranulates to break down cell by apoptosis
Function of NK cells
Activate macrophages
Death receptors
Release cytokines to communicate with other cells
Which is the rarest granulocyte?
Basophil
What do basophils do?
Acute and chronic allergic response
Contribute to resistance to internal parasites
Why do basophils have their name?
Take up basic dyes
Where are eosinophils mainly found?
Gut and lymphatic system
Why do eosinophils appear pink under a microscope?
Take up acidic dye eosin
What do eosinophils do?
Participate in allergic disease and helminth infections
Release cytokines to attract cells of immune system
What is pattern recognition?
PRR receptors on surface of innate cells
PRR recognise PAMP
Adaptive cells use antibodies and t-cell receptors to recognise PAMP
What does PAMP stand for?
Pathogen Associated Molecular Pattern
Examples of PAMP in bacteria
Peptidoglycan
Lipiprotein
Flagellum
DNA
Examples of PAMP on viruses
DNA
RNA
What does TLR stand for?
Toll-like receptors
Where are TLRs expressed from?
Macrophages
Dendritic cells
What do TLRs do?
Recognise different pathogens
Activate APCs to produce pro-inflammatory cytokines and stimulate co-stimulatory molecule expression
What is another name for TLRs?
PRR
Where is C-reactive protein produced?
Liver
What type of protein is c-reactive protein?
Acute phase protein
What can CRP level be used to measure?
Inflammation
What does CRP do?
Enters tissue and activates immune cells/opsonize pathogen to make it more visible to the immune system
What are the three pathways in the complement protein cascade?
Lectin
Classical
Alternative
What is the lectin pathway in the complement protein cascade?
Iniated by lectin binding proteins and ficolin MASP binding to carbohydrates on pathogens
Produces C3 convertase
What is the classical pathway in the complement protein cascade?
Initiated by C1Q binding to pathogen. Produces C3 convertase
What is the alternative pathway in the complement protein cascade?
C3 complement protein binds to carbohydrate on pathogen surface
C3b produced, which binds with other factors to produce C3 convertase
What do complement proteins do?
Means our cells are lysed - membrane attack complex forms (complement protein makes holes in target cell)
Activates inflammatory response and membrane attack complex
Act as signalling molecule
Cell clearance
What happens when a pathogen is opsonised?
Makes it more visible to innate cells
What happens when a membrane attack complex is formed?
Pores formed in surface of pathogen so it bursts and loses its contents
Antimicrobial proteins in the innate immune system
Antibodies/lytic enzymes/interferons/cytotoxins
complement
Inflammatory proteins in the innate immune system
Cytokines/chemokines/histamines
What is the common end product of the complement system?
C3 convertase
