Chapter 15 Flashcards
host defence mechanisms
- ways in which the body protects itself from pathogens
- 3 lines of defence
lines of defense
- first 2 are non specific
- third is specific, the immune response
third line of defense
- antibodies are produced in response to antigens
- the immune system, lymphocytes
second line of defence
cellular
- inflammation
- phagocytosis
- transferrin
- fever
- interferons
- complement system
- acute-phase proteins
- cytokines
first line of defence
acellular
- intact skin
- mucous membranes
- cellular and chemical factors
- microbial antagonism
non-specific host defence mechanisms
- general and serve to protect body against harmful substances
- innate or inborn resistance, mechanical and physical barriers, chemical factors, microbial antagonism, fever, inflammation, phagocytosis
physical barriers
- skin and mucous membranes
cellular and chemical factors
- pH, temperature, perspiration, cilia, and enzyme secretions
- components of first line
microbial antagonism
- when indigenous microbiota prevent colonization of bacteria as a result of competition for sites and nutrients and production of lethal substances
transferrin
- a glycoprotein
- levels increase in response to bacterial infection
- binds to iron to deprive pathogens of it
fever
- stimulated by progenies substances like pathogens and interleukin 1 (IL1)
- increases hosts defences by stimulating leukocytes, reducing available iron, and inducing production of IL-1
interferons
- small antiviral proteins produced by virus infected cells that prevent viruses form multiplying
- no virus specific but species specific
- can cause nonspecific flu like symptoms
3 types of interferons
- alpha
- beta
- gamma
- they are induced by different stimuli like viruses, tutors, bacteria, and foreign cells
the complement system
- group of 30 different proteins found in normal blood plasma
- assists in destruction of many different pathogens
- complementary to immune system
complement cascade
when complement components interact with each other in a stepwise manner
opsinization
- process where phagocytosis is facilitated by the deposition of options which are antibodies or complement fragments onto pathogens
- it labels the pathogen for phagocytosis
acute-phase proteins
- plasma proteins that increase rapidly in response to infection, inflammation, or tissue injury
cytokines
- chemical mediators released from body cells
- enable cells to communicate with each other within the immune system and between immune and other body systems
chemoattractants
- type of cytokine called chemokines
- they recruit phagocytes to sites where they are needed
inflammation
- when the body responds to any injury, irritation, microbial invasion, or bacterial toxin by a complex series of events
3 major events of inflammation
1) capillary vasodilation to increase BF
2) increased permeability of capillaries for escape of plasma and plasma proteins
3) exit of leukocytes from capillaries and their accumulation at injury site
primary purposes of inflammation
- localize infection
- prevent spread of microbial invaders
- neutralize toxins being produced at the site
- aid in repair of damaged tissue
4 major signs and symptoms of inflammation
- redness
- heat
- edema
- pain
what causes edema
plasma that escapes from the capillaries into the site
sequence of events in inflammation
1) tissue injury
2) vasodilation
3) increased permeability
4) emigration of leukocytes from blood vessel to tissue
5) chemotaxis
6) phagocytosis
inflammatory exudate
- the accumulation of fluid, cells, and cellular debris at the inflammation site
purulent exudate
- pus
- thick and green-yellow exudate with many live and dead leukocytes
pyogenic microbes
- result in additional pus formation
- staphylococci and streptococci
phagocytes
- phagocytic white blood cells
phagocytosis
- the process by which phagocytes surround and engulf foreign material
3 major leukocytes
- monocytes
- lymphocytes
- granulocytes (eosinophils, basophils, neutrophils)
macrophages
- phagocytosis
- stimulates rest of immune system to respond
- antigen presenting cell
neutrophils
- phagocytize
- release toxin that kills surrounding tissue
most important groups of phagocytes in human body
- macrophages and neutrophils
4 steps in phagocytosis
1) chemotaxis
2) attachment
3) ingestion
4) digestion
chemotaxis
- phagocytes are attracted by chemotactic agents to site
attachment
phagocyte attaches to object
ingestion
pseudopodia surround object and it is taken into the cell
digestion
object is broken down and dissolved by digestive enzymes and other mechanisms
mechanisms by which pathogens escape phagocytosis
- capsules serve to protect organism
- some bacteria produce exoenzyme leukocidin which kills phagocyte
- some bacteria like M TB are not destroyed within phagolysosome
- mechanisms by which each pathogen evades digestion by lysosomal enzymes is different for each pathogen
disorders that affect immune resposne
- leukopenia
- disorders affecting leukocyte motility and chemotaxis (related to actin defect)
- disorder affecting intracellular killing by phagocytes (chronic granulomatous disease)
leukopenia
- abnormally low number to circulation leukocytes
other factors affecting immune response (8)
- nutritional status
- increased iron levels
- stress
- cancer and chemo
- genetic defects
- age
- AIDS
- drugs
