innate immunity Flashcards
define immune system
cells and organs that contribute to immune defences against infectious and non infectious (cancer) conditions
define infectious disease
when the pathogen succeeds in evading and/or overwhelming the host’s immune defences
what are the roles of the immune system
pathogen recognition
containing/eliminating the infection
regulating itself- minimum damage to self
remembering pathogens
what are the two types of immune response and what’s the difference
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
what barriers does innate immunity consist of?
physical
physiological
chemical
biological
what are the physical barriers provided by innate immunity?
skin
mucous membranes- mouth, respiratory tract, GI tract &urinary tract
bronchial cilia
what are the physiological barriers provided by innate immunity?
diarrhoea- food poisoning
vomiting- food poisoning, hepatitis, meningitis
coughing- pneumonia
sneezing -sinusitis
what are the chemical barriers
low pH antimicrobial molecules- IgA(immunoglobin A):tears, saliva, mucous membrane) lysozyme (sebum, sweat,urine) mucus beta-defensins(epithelium) gastric acid +pepsin
what are the biological barriers
normal flora in strategic locations
absent in internal organs/tissues
what are the benefits of normal flora
compete with pathogens for attachment sites and resources.
produce antimicrobial chemicals
synthesise vitamins (K ,B12, other B vitamins)
how can normal flora cause clinical problems
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
what are the second lines of defence(innate immunity)
phagocytes and chemicals causing inflammation
what are the main types of phagocytes
macrophages , monocytes and neutrophils
function of macrophages
present in all organs.
phagocytosis- ingest and destroy microbes
present microbial antigens to T cells
produce cytokines/chemokines
function of monocytes
recruited at infection site and differentiate into macrophages
function of neutrophils
recruited by chemokine to site of infection
ingest and destroy pyogenic bacteria
name cells other than phagocytes involved in innate immunity
basophils/mast cells
eosinophils
natural killer cells
dendritic cells
how do phagocytes recognise pathogen
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
name some examples of opsonins
complement proteins- C3b, C4b
antibodies-IgG,IgM
Acute phase proteins: C-reactive protein(CRP), Mannose-binding lectin(MBL)
how do phagocytes destroy microbes
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
name some proteins from the complement system and their function
C3a and C5a- recruitment of phagocytes
C3b- opsonisation of pathogens
C5-C9: killing of pathogens via membrane attack complex
state some antimicrobial actions of cytokines
liver-produce CRP &MBL
bone marrow - neutrophil mobilisation
hypothalmus -increase body temp
blood vessels -vasodilation, vascular permeability and expression of adhesion molecules
State some clinical problems when phagocytosis is reduced
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)
