Non-specific animal defences against pathogens Flashcards Preview

Chapter 12 Communicable Disease > Non-specific animal defences against pathogens > Flashcards

Flashcards in Non-specific animal defences against pathogens Deck (14):

What are non-specific defences?

-Always present and activated rapidly in animals.
-Defends against all pathogens in same way.


What is the specific immune response?

-Specific to each pathogen and slower to respond.


What non-specific defences keep pathogens out?

-Body barriers.
-Blood clotting and wound repair.
-Inflammatory response.


What body barriers keep pathogen out?

-Skin; covers body and has a skin flora of healthy microorganisms that outcompete pathogens for space. Skin also produces sebum which inhibits growth of pathogens.
-Tears and urine; have lyzozymes which destroy microorganisms.
-Mucus and cilia; mucus traps microorganisms and contains lysozymes and phagocytes. Cilia move microorganisms along.
-Coughs and sneezes; eject pathogen mucus from gas exchange.


How does blood clotting and wound repair keep pathogens out?

-When platelets come into contact with collagen in skin they adhere and secrete substances like; thromboplastin which is an enzyme that triggers a cascade of reaction resulting in blood clot. Also, serotonin which makes smooth muscle in blood vessel walls contract and reduce supply of blood.
-Clot dries and scab forms, epidermal cells and blood vessels regrow and collagen fibres are deposited to give strength.
-Normal epidermis is reached and scab falls off.


What is the inflammatory response?

-Response to pathogens resulting in inflammation, pain, heat and redness.


How does the inflammatory response work?

-Mast cells activated in damaged tissue and release chemicals called histamines and cytokines.
-Histamines; make blood vessels dilate and cause heat and redness, heat reduces pathogens reproducing. Also, make blood vessel walls more leaky and force out blood plasma this causes swelling.
-Cytokines; attract white blood cells (phagocytes) to the site, destroy pathogens by phagocytosis.


What are the non-specific defences that get rid of pathogens?



How do fevers get rid of pathogens?

-Raise in temperature is useful because, inhibits pathogen reproduction and specific immune system works faster.


What are phagocytes?

-Specialised white blood cells that engulf and destroy pathogens, two types; neutrophils and macrophages.
-Phagocytes build up at infection site and attack pathogens.


What are the stages of phagocytosis?

-Pathogens produce chemicals that attract phagocytes.
-Phagocytes recognise pathogen as non-self.
-Phagocyte engulfs pathogen and encloses it in a vacuole called phagosome.
-Phagosome combines with lysosome and forms phagolysosome.
-Enzyme from lysosome digest and destroy pathogen.


How are APC's formed?

-If a macrophage digests pathogen, it combines antigen from pathogens membrane with MHC (major histocompatability complex).
-MHC moves antigens to macrophages membrane and becomes an APC.
-Antigens now stimulate other cells involves in specific immune response.


What are cytokines?

-Phagocytes that engulf pathogen produce these.
-Act as cell-signalling molecules that inform other phagocytes that body is under attack.
-Also increase body temperature and stimulate specific immune system.


What are opsonins?

-Chemicals that bind to pathogens and 'tag' them, so can be easily recognised by phagocytes.
-Phagocytes have receptors on cell membrane that bind to common opsonins and the phagocyte engulfs the pathogen.