Session 3-Innate Immunity Flashcards
Define immune system
Cells and organs that contribute to immune defences against infectious and non-infectious conditions
What is an infectious disease?
When the pathogen succeeds in evading and/or overwhelming the host’s immune defences
What are the roles of the immune system? (4)
1) pathogen recognition
2) containing/eliminating infection
3) regulating itself
4) remembering pathogens
True or false: innate immunity provides long lasting protection
FALSE - immediate protection
What are the innate physical barriers?
1) skin
2) mucous membranes
3) bronchial cilia
What are the innate physiological barriers and what are they barriers against?
1) diarrhoea - food poisoning
2) vomiting - food poisoning, hepatitis, meningitis
3) coughing - pneumonia
4) sneezing - sinusitis
What are the innate chemical barriers?
1) low pH
2) antimicrobial molecules
What is the pH of skin?
5.5
What is the pH of the vagina?
4.4
What are normal flora?
Biological barrier, non-pathogenic microbes in strategic locations
True or false: normal flora is present in internal organs/tissues
FALSE - absent
Where are normal flora present?
Nasopharynx Mouth/throat Skin GI tract Vagina
What are the benefits of normal flora? (3)
1) Compete with pathogens for attachment sites and resources
2) Produce antimicrobial chemicals
3) Synthesise vitamins
Which normal flora inhabits the skin?
Staphylococcus aureus
Which normal florae inhabit the nasopharynx?
Streptococcus pneumoniae
Neisseria meningitidis
When do clinical problems start with normal flora? (3)
1) when normal flora is displaced from its normal location to a sterile location
2) when normal flora overgrows and becomes pathogenic when the host becomes immuno-compromised
3) when normal flora is depleted by antibiotics
In which ways can normal flora be displaced from its normal location? (3)
1) breaching skin integrity through burns, surgery, injections etc
2) fecal-oral route (foodborne)
3) fecal-perineal-urethral route (UTI)
Which microbe causes vaginal thrush?
Candida albicans
What are the three main types of phagocytes?
1) macrophages
2) monocytes
3) neutrophils
Which phagocyte is present in pus?
Neutrophils
What are the function of macrophages? (3)
1) phagocytosis
2) present microbial antigens to T cells
3) produce cytokines/chemokines
What do monocytes differentiate into?
Macrophages
When is the level of neutrophils increased?
During infection
What is the function of neutrophils?
Ingest and destroy pyogenic bacteria
Which other key cells are involved in innate immunity? (4)
1) basophils/mast cells
2) eosinophils
3) natural killer cells
4) dendritic cells
Complete the sentence:
Microbial structures have PAMPs (_________-_____________ __________ __________) which are recognised by PRRs (________ _____________ __________) on phagocytes.
Pathogen-associated molecular patterns
Pathogen recognition receptors
Why are PRRs present inside the cell as well as on the surface?
Viruses replicate inside cells so to recognise viruses
How does opsonisation of microbes take place?
Coating proteins called opsonins bind to microbial surfaces, leading to enhanced attachment of phagocytes and clearance of microbes
Give examples of opsonins
1) Complement proteins eg C3b
2) Antibodies eg IgG
3) Acute phase proteins eg CRP and mannose-binding lectin (MBL)
What are the two activating pathways of the complement system and what are they initiated by?
1) alternative pathway-initiated by cell surface microbial constituents
2) Mannose-binding lectin pathway-initiated when MBL binds to mannose containing residues of proteins found on microbes
What are the antimicrobial actions of C3a and C5a complement proteins?
Recruitment of phagocytes (chemoattractants)
What are the antimicrobial actions of C3b-C4b?
Opsonisation of pathogens
What are the antimicrobial actions of C5-C9?
1) Killing of pathogens
2) Membrane attack complex (form pores which punch holes in bacterial cell wall and kill bacteria)
What is released by activated macrophages?
Tumour necrosis factor (TNFa)
Interleukins (IL-1/IL-6)
What are the antimicrobial actions of macrophage-derived TNFa/IL-1/IL-6 in the liver?
CRP
Mannose binding lectin -> complement activation
What are the antimicrobial actions of macrophage-derived TNFa/IL-1/IL-6 in bone marrow?
Neutrophil mobilisation
What are the antimicrobial actions of macrophage-derived TNFa/IL-1/IL-6 in the inflammatory response?
Vasodilation
Vascular permeability
Adhesion molecules -> attraction of neutrophils
What are the antimicrobial actions of macrophage-derived TNFa/IL-1/IL-6 in the hypothalamus?
Increased body temperature
Which clinical problems start with reduced phagocytosis?
1) Decreased spleen function
2) Decreased neutrophil number
3) Decreased neutrophil function
