Principles - Innate Immune System 1) Leukocytes Flashcards
What are the 3 main functions of the innate immune system.
- identification of microorganisms
- rapid destruction and clearance
- stimulation of adaptive system
What is the main target of neutrophils?
bacteria and fungi
What are the main functions of eosinophils?
target large parasites and modulate allergic responses
What do basophils and mast cells do?
release histamine for inflammatory responses
Which out of basophils and mast cells leaves the bone marrow already mature and which circulates in an immature form (only maturing once in a tissue site)?
basophils leave bone marrow already mature
mast cells circulate immature
What do B lymphocytes do?
release antibodies
assist in T cell activation
What are NK cells?
virus infected and tumour cells
What do macrophages do?
phagocytosis
stimulate lymphocytes and other immune cells
What do dendritic cells do?
act as antigen-presenting cells, activating T lymphocytes
Which lymphocytes are linked to asthma and allergy?
eosinophils
What are the first line of defence against bacteria/fungi?
phagocytes
Where do neutrophils and monocytes carry out phagocytosis?
circulation
Where do macrophages and dendritic cells carry out phagocytosis?
tissues
What are polymorphonuclear cells?
neutrophils
What is the leukocyte largest in number?
neutrophils
Do neutrophils circulate freely in the blood?
Yes
What are the first line of defence at sites of damage or infection?
neutrophils
What are circulating monocytes precursors of?
tissue macrophages
Where are monocytes and macrophages produced?
bone marrow
Do dendritic cells phagocytose as immature or mature cells?
immature
When do dendritic cells start to mature?
as they respond to inflammatory indicators
What happens to dendritic cells as they start to mature?
lose phagocytotic activity, migrate to lymph nodes, present antigen to T lymphocytes
What do phagocytes produce?
cytokines
Are macrophages destroyed during phagocytosis?
No
What are used to recognise pathogen associated molecular patterns?
pathogen recognition receptors
What are PAMPs?
pathogen associated molecular patterns - expressed by microorganisms, but not by human cells
What is the PAMP in bacterial loppolysaccharides?
binds to toll-like receptor 4, which is a Pathogen recognition receptor expressed on macrophages and dendritic cells
What do opsonins do?
act as a bridge between the pathogen and the phagocyte receptors, facilitating uptake of microorganisms
What are the main opsonins?
Fc fragment of IgG
C3b
Collectins
What is C3b?
fragment of C3 generated by compliment activation
What are collectins?
plasma proteins that bind to microbial cells walls
What are microorganisms coated with to facilitate phagocytosis?
proteins e.g. acute phase proteins, antibodies and complement proteins
What type of protein is C reactive protein?
acute phase protein
What are the two types of killing in phagocytosis?
oxidative and non oxidative
What is oxidative killing especially important for?
neutrophils
What crucial enzyme is involved in oxidative killing?
NADPH oxidase complex
What does NADPH oxidase complex do?
converts oxygen into reactive oxygen species - hydrogen peroxide, superoxide 02 and hypochlorite H0Cl, which are lethal to microorganisms
What does non oxidative killing involve?
Can kill bacteria inside cell and in local environment
Bacteridical enzymes released e.g. defensins, lysozomes, collagenase and lactoferrin
What does lactoferrin do?
collect iron as lots of bacteria depend on iron for their metabolism
Where are the bactericidal enzymes made?
in lysosomes and neutrophil secondary granules
What does phagocytosis do to neutrophils?
glycogen reserves are depleted, neutrophils die, formation of pus occurs
What do primary granules of neutrophils do?
kill ingested microbes, digest their remains. Granules fuse with phagoctyic vesicles containing enzymes
What are ensymes like myeloperoxidase very good at generating?
free radicals
What is movement toward or away from a chemical stimulus called?
chemotaxis
What happens in patients with phagocyte deficiencies?
reccurent deep bacterial and fungal infections, often poorly responsive to antibiotics
