innate immunity

Question 1

define immune system

Answer 1

cells and organs that contribute to immune defences against infectious and non infectious (cancer) conditions

Question 2

define infectious disease

Answer 2

when the pathogen succeeds in evading and/or overwhelming the host’s immune defences

Question 3

what are the roles of the immune system

Answer 3

pathogen recognition
containing/eliminating the infection
regulating itself- minimum damage to self
remembering pathogens

Question 4

what are the two types of immune response and what’s the difference

Answer 4

innate immunity and adaptive immunity
innate- immediate protection:fast, lack of specificity and memory, no change in intensity
adaptive- long lasting protection:slow, specificity, immunologic memory, changes in intensity

Question 5

what barriers does innate immunity consist of?

Answer 5

physical
physiological
chemical
biological

Question 6

what are the physical barriers provided by innate immunity?

Answer 6

skin
mucous membranes- mouth, respiratory tract, GI tract &urinary tract
bronchial cilia

Question 7

what are the physiological barriers provided by innate immunity?

Answer 7

diarrhoea- food poisoning
vomiting- food poisoning, hepatitis, meningitis
coughing- pneumonia
sneezing -sinusitis

Question 8

what are the chemical barriers

Answer 8

low pH 
antimicrobial molecules- IgA(immunoglobin A):tears, saliva, mucous membrane)
lysozyme (sebum, sweat,urine)
mucus 
beta-defensins(epithelium)
gastric acid +pepsin

Question 9

what are the biological barriers

Answer 9

normal flora in strategic locations

absent in internal organs/tissues

Question 10

what are the benefits of normal flora

Answer 10

compete with pathogens for attachment sites and resources.
produce antimicrobial chemicals
synthesise vitamins (K ,B12, other B vitamins)

Question 11

how can normal flora cause clinical problems

Answer 11

when they are displaced from normal location to sterile location
breaching skin integrity- skin loss(burns), surgery, IV lines, skin diseases , injection drug users and tattoo/piercing
fecal-oral route
fecal-perineal-urethral route (UTI)
poor dental hygiene/dental work

Question 12

what are the second lines of defence(innate immunity)

Answer 12

phagocytes and chemicals causing inflammation

Question 13

what are the main types of phagocytes

Answer 13

macrophages , monocytes and neutrophils

Question 14

function of macrophages

Answer 14

present in all organs.
phagocytosis- ingest and destroy microbes
present microbial antigens to T cells
produce cytokines/chemokines

Question 15

function of monocytes

Answer 15

recruited at infection site and differentiate into macrophages

Question 16

function of neutrophils

Answer 16

recruited by chemokine to site of infection

ingest and destroy pyogenic bacteria

Question 17

name cells other than phagocytes involved in innate immunity

Answer 17

basophils/mast cells
eosinophils
natural killer cells
dendritic cells

Question 18

how do phagocytes recognise pathogen

Answer 18

microbial structures have pathogen-associated molecular patterns(PAMPs):carbs, lipids.proteins &nucleic acids
Phagocytes have pathogen recognition receptors (PRRs):toll like receptors
opsonisation -coating proteins called opsonins that bind to the microbial surfaces leading to enhanced attachment of phagocytes and clearance of microbes

Question 19

name some examples of opsonins

Answer 19

complement proteins- C3b, C4b
antibodies-IgG,IgM
Acute phase proteins: C-reactive protein(CRP), Mannose-binding lectin(MBL)

Question 20

how do phagocytes destroy microbes

Answer 20

once the phagocyte has recognised and bound to the microbe via PAMP to PRR interactions and the opsonin to opsonin receptor interactions it can now be destroyed by engulfment and digestion.
this can either happen by an oxygen dependant pathway- free oxygen radicals
or a oxygen independent pathway- enzymatic digestion

Question 21

name some proteins from the complement system and their function

Answer 21

C3a and C5a- recruitment of phagocytes
C3b- opsonisation of pathogens
C5-C9: killing of pathogens via membrane attack complex

Question 22

state some antimicrobial actions of cytokines

Answer 22

liver-produce CRP &MBL
bone marrow - neutrophil mobilisation
hypothalmus -increase body temp
blood vessels -vasodilation, vascular permeability and expression of adhesion molecules

Question 23

State some clinical problems when phagocytosis is reduced

Answer 23

decrease spleen function- asplenic and hyposplenic patients
decrease neutrophil function- cancer chemotherapy , certain drugs, leukaemia and lymphoma
decreased neutrophil function- chronic granulomatous disease (no respiratory burst) and chediak-higashi syndrome (no phagolysosome formation)