Innate immune system Flashcards
Blood composition
blood is composed of plasma and cells erythrocytes (RBC) Leukocytes (WBC) platetes (clotting) water -91% proteins
Erythroid
red blood cells
Myeloid
granulocytes, monocytes, dendritic cells, platelets (innate immune cells)
Lymphoid
B and T lymphocytes (adaptative immune cells) - kill other cells
3 blood cell types
Erythroid
Myeloid
Lymphoid
all of these are derived from hematopoietic stem cells in the bone marrow
neutrophils
75% of leukocytes (granulocytes) in the blood
highly phagocytic - eat and kill
numbers increase during infection
Eosinophils
1-6% of leukocytes (granulocytes) in the blood
release toxic granules to kill parasite
numbers increase in blood during parasitic infection
Basophils
0.5% of leukocytes (granulocytes) in the blood
release granules that can mediate allergic reactions or fight infection really uncommon to see in a blood smear
granulocytes
circulate in the blood and can move into tissue during inflammation/ infection
granulocytes in tissue
mast cells line mucosal surfaces (not found in blood)
release granules that attract white blood cells to areas of tissue damage
Monocytes and macrophages
monocytes present in blood - low phagocytosis
leave blood - develop into macrophages in tissue eg spleen and liver. - high phagocytosis
monocytes have a large nucleus, in tissue the then go into macrophages and become highly phagocytic and eat anything.
macrophages
become resistant (sessile) or move through tissue (migratory)
3 important functions
- phagocytosis
- release of chemical messengers
- show information about pathogenic microbes to T cells (linking innate and adaptive immunity)
alert other immune cells when where is an infection
Dendritic cells
found in low numbers in blood and all tissues in contact with the environment
phagocytic
most important cell type to trigger adaptive immune response
very potent so don’t need many of them`
How do immune cells move around the body?
cells are carried in the blood and in the lymph
cells can leave he blood and enter tissues when they get the right signals
lymph tissue collects into lymphatic vessels. these drain into lymph nodes
4 cardinal signs of inflammation
heat redness swelling pain vasodilation, leaky blood cells allow cells to get from blood into tissue and help us fight any invading organisms. this leads to swelling as there are a lot of cells going to that place and leads to heat production and the whole process is painful. also a loss of function because of this.
fever (heat)
temp above 37
re-setting of thermostat (hypothalamus)
pyrogens make us hot
phagocyte produce a chemical messenger and pyrogen interleukin-1 after ingesting bacteria
a decrease in phagocytosis will lead to a decrease in the release of L-1 and that will lead to a decrease in temperature
inflammatory response 1
mast cells - granular cites and have preformed vesicles that are able to be released upon damage or exposure to pathogens
macrophages- come along and phagocytose
mast cells release
histamine - vasodilation of blood vessels
prostaglandins and leukotrienes - vascular permeability of blood vessels
all of these are within the vesicles in the mast cells
inflammatory response 2
the vessels become permeable and more blood flow makes injury red. the white blood cells can now squeeze through the walls of the blood vessel and to the tissue where it has been injured because of increased permeability.
phagocytes (neutrophils) come along from the blood stream and clean up any left over pathogens in the injury area. these can lead to puss over a clearance of infection.
response to virus
innate antiviral protein - type 1 interferon (TFN)
type 1 interferon (IFN)
is a chemical messenger or cytokine produced by many host cells to combat viruses
cells communicate to each other by telling each other there is a virus and this limits the spread of infection
the cells destroy RNA and reduce protein synthesis
signalling neighbouring to undergo apoptosis
activates immune cells
Toll-like receptors
pattern recognising receptors in or on innate cells
bind to common microbial molecular patterns
TLR engagement drives many innate immune mechanisms
like phagocytosis, cytokine release, interferon release
some are in cell membranes and some are on the inside.
TLR 4 and 5
are on the cell membrane and send inflammatory signals to the inside of the cell
TLR 9 and 3
are in the nucleus
9 binds to bacterial DNA
3 binds to viral double stranded RNA.
inflammatory responses are triggered
stages of phagocytosis `
- pseudopodia (false foot come out) surrounds microbes gives them a hug.
- microbes are adhered to phagocyte and are engulfed
- ingestion of microbes into vacuole ie. phagosomes
- fusion of vacuole and lysosome (has digestive enzymes and low pH to kill)
- killing and digestion of microbe
- elimination (exocytosis) of dead microbe, like waste produce of phagocyte
killing and digestion of phagocytosed microbes
low pH - acid environment reactive oxygen (hydrogen peroxide) and reactive nitrogen intermediates enzymes - protease - break down proteins - lipase - break down lipids - nuclease - break down nuclear material
the complement cascade
complement - 9 major proteins/ protein complexes.
act in a sequence to clear pathogens from blood and tissue
label - opsonisation
recruitment - chemotaxis
destroy - lysis
3 complement pathways
classical - antibody bound to pathogen binds to complement
alternative - pathogen binds to complement to surface/ pathogen
lectin - carbohydrate components of microbes bind to complement
3 outcomes from the complement cascade
label
destroy
recruit
label (complement cascade)
opsonisation = coating of microbe with an antibody and or complement fragment C3b
leads to uptake by phagocyte, can lead it with antibody leads to destruction
destroy (complement cascade)
membrane attack complex formation -pores in bacterial cells causes water to rush in and cause lysis of the cell and destruction. initiated by microbe being covered with C9.
recruit (complement cascade)
phagocytes are attracted to the site
mast cells degranulated by C3a and C5a
inflammatory mediators released including proteins that attract phagocytes - chemical trail.
