INNATE IMMUNITY AND THE INFLAMMATORY PROCESS Flashcards
how is skin a physical barrier to pathogens?
it has many layers of keratinised cells and the periodic shedding helps to remove pathogens from the surface. the skin also has glands which secrete sebaceous oil which inhibits the growth of certain pathogens.
how are mucous membranes a first line of defence? give examples
the mucous is slightly viscous so traps many microbes. e.g. in the nose there is also hairs, in the upper respiratory tract there is also cilia and swallowing mucous can take pathogens to the stomach where the gastric juice destroys them
how do eyes defend against pathogens?
the lacrimal apparatus manufactures and drains away tears in response to irritants. lining spread tears over the surface of the eye, diluting pathogens and keeping them from settling on the surface. tears contain lysozymes
what are some first line defences against pathogens?
skin, mucous membranes, tears, saliva, urine, vaginal secretions, sneezing, coughing, defecation, vomiting, perspiration, gastric juice
what are interferons?
proteins that diffuse to uninfected cells and induce synthesis of antiviral proteins to interfere with viral replication.
what releases interferons?
lymphocytes macrophages and fibroblasts infected with viruses can release them.
what can iron-building proteins do to defend against pathogens? give some examples
inhibit the growth of certain bacteria by reducing the amount of iron available. e.g. transferrin, lactoferrin, ferritin and haemoglobin
what do antimicrobial proteins do?
they kill microbes, attract dendritic cells and mast cells to participate in an immune response.
where can we find natural killer cells?
blood, spleen, lymph nodes and red bone marrow
describe the steps of a natural killer cell?
NK cells bind to target cells and this causes the release of cytotoxic granules from NK cells. some granules contain perforin which inserts into the plasma membrane of the target cell and created perforations. as a result, extracellular fluid flows into the target cell and the cell bursts. other granules may release granzymes which induce the cell to undergo apoptosis.
what can natural killer cells release?
granzymes or perforin
what is an issue with natural killer cells?
they kill the infected cell but do not destroy the microbes inside so when the cell bursts/dies these microbes are released and must be destroyed by phagocytes
describe the 2 different types of macrophages?
when an infection occurs, monocytes migrate to this area and enlarge and develop into actively phagocytic macrophages whereas other macrophages can be fixed and stand guard in specific tissues.
describe the steps taken in phagocytosis?
- chemotaxis= phagocytes are attracted to the site of damage by chemicals.
- adherence= the phagocyte attaches to the microbe via PAMP
- ingestion= the plasma membrane of the phagocyte extends projections called pseudopods that engulf the pathogen by surrounding it and fusing
- digestion = phagosome merges with lysosome to form phagolysosomes. the lysosomes break down microbial cell walls and degrade the insides. respiratory burst can also happen here
- killing= any material not degraded further by the above is called residual bodies
describe the respiratory burst?
its a rapid increase in the production of reactive oxygen species during phagocytosis. the immune cells use NADPH oxidase to reduce O2- to an oxygen free radical and then to H2O2. these damage microbial membrane and can activate microbicidal enzymes.
describe the 3 stages of the inflammatory response?
vasodilation and increased permeability of blood vessels
emigration of phagocytes from the blood into the interstitial fluid
tissue repair
after tissue injury, what immediate changes do we get in the blood vessels?
vasodilation of arterioles to allow more blood to damaged area
increased permeability of capillaries so defensive proteins can enter the injured area from the blood
what cells release histamine? what is the effect?
mast cells, basophils, platelets, neutrophils and macrophages. it causes vasodilation and increased permeability of blood vessels.
What effect do kinins have? give an example of one
they induce vasodilation and increase permeability and serve as chemotactic agents for phagocytes. e.g. bradykinin