immune system I - innate immune system Flashcards
whats the sequence of events in inflammation that lead up to phagocytosis?
- defence by resident macrophages
- localised vasodilation
3.increased capillary permeability - localised oedema walling
- walling off of the inflamed area
- emigration of leukocytes
- phagocytosis
step 2: how is localised vasodilation induced and what happens in it
induced by mast cells degranulation
1.immediate arteriole dilation
2. increased local blood supply
3. increased number of phagocytes and plasma proteins
step 2: what happens when capillary permeability increased
- histamine-induced widening of capillary pores
- escape of plasma proteins
- increased osmotic pressure
- escape of accompanying fluid
step 4: what happens in localised oedema and what are the consequences?
- excessive fluid accumulation
- leads to localised oedema = swelling
consquences:
-increased distance between blood and cells so decreased diffusion rate of nutrients, o2 and waste hence reduced supply
in step 5 what happens in walling off of the inflamed area
- leaked plasma proteins are exposed to tissue so clotting and anticlotting factors of fibronectin are leaked
- fibrinogen is the final factor
- fibrin forms clots around the invader and or damaged cells to prevent spread of invader or toxic products
- inflamed area is walled off
step 6 what happens in emigration of leukocytes?
- in migration and adhesion, CAMs and integrins mean leukocytes are concentrated next to endothelial cells
- diapedesis where leukocytes squeeze through capillary pores
- chemotaxis occurs
how does target recognition in phagocytosis occur?
- surface characteristics such as roughness
- bacterial cell components - saccharides
- chemical mediator coats of opsonins such as C3b
what are the steps of phagocytosis?
- phagocyte membrane binds to bacteria
- releases the oxygen radicals of O2-.,OH., O and the cell surface membrane and in inner phagosome
- phagosome and the lysosome fuse
- discharge of acid and bactericidal enzymes
what are the bactericidal mechanisms of phagocytes?
-reactive oxygen intemediates
-lethal acidity in phagolysosomes
-lysozyme
-lysosomes contain lethal cationic proteins like lactoferrin
-catalase
-glutathione peroxidase
what happens to phagocytes as a result of their bactericidal mechanisms?
-accumalate toxic by-products
-lysosomal chemical release of cytosol causes phagocyte death
-pus production which is a collection of phagocytes, liquefied necrotic tissue and bacteria
what are the detrimental effects of phagocytosis?
- pus causes tissue destruction to bacteria spread and painful
-liberation of phagocyte lysosomal enzymes causes cell destruction and inflammation
-certain intracellular organisms thrive inside macrophages causing satellite infections such as TB and leprosy
which leukocytes undergo exocytosis and how
macrophages, eosinophils and neutrophils
1. flattening of cell membrane towards the large enemy
2. fusion of lysosomal and cell membranes
3. spit out oxygen free radicals/ lysosomal enzymes
what do natural killer cells do and how do they undergo exocytosis?
immediate, non-specific destruction of virus-infected/ cancer cells
exocytosis:
1. attach via lectins to enemy target
2. exocytose perforin onto cell surface
3. membrane puncture
4. cell lysis or induced apoptosis of infected cell
give 3 features of interferon
-nonspecific resistance to viral infections
-interferes with viral replication
-1st line of viral defence
how does interferon reinforce other immune activities?
- enhances macrophage activity
- stimulates antibody production
- suppresses cell division - tumour growth
- enhances NK cell and cytotoxic T cell function
overall forms anti viral and anti cancer effects
