Session 3 - Innate Immune system Flashcards
What 2 components is the immune response made up of?
Innate and adaptive immunity
What are the 4 first line defences of innate immunity? What is its purpose?
1) Physical barriers
2) Physiological barriers
3) Chemical barriers
4) Biological barriers Serves to limit entry and growth of pathogens
What are the physical barriers?
- Skin
- Mucous membranes – in mouth, resp tract, GI tract, urinary trat
- Bronchial cilia
What are the physiological barriers?
- Diarrhoea – food poisoning, allergies
- Vomiting – food poisoning, meningitis
- Coughing – pneumonia
- Sneezing – sinusitis
What are the chemical barriers?
- Low pH – skin (5.5), stomach (1-3), vagina (4.4)
- Antimicrobial molecules – in tears, saliva, perspiration, urine, epithelium
What are the biological barriers?
Normal flora – non pathogenic microbes in strategic locations, e.g. nasopharynx, mouth, skin, vagina, GI, but absent in internal organs
o Benefits by competing with pathogens for attachment sites and resources o Producing antimicrobial chemicals
o Synthesising vitamins (K and B12)
With regards to normal flora, when do clinical problems occur?
1) When flora displaced from original location to sterile location.
2) When host is immunocompromised and normal flora overgrows and becomes pathogenic
3) When normal flora is depleted by AnB e.g. thrush
What is Innate Immunity’s second lines of defence? What is its purpose?
- Phagocytes
- Chemicals – comprised of the complement system and cytokines Both of which lead to inflammation.
The second line of defence contain and eliminate the infection.
What is the function of a phagocyte? What are the 3 main types and what do they do?
Recognising and killing MOs.
1) Macrophages - Produce cytokines and phagocytose microbes
2) Monocytes - Differentiate into macrophages
3) Neutrophils - Ingest and destroy pyogenic bacteria
How do phagocytes recognise microbes?
PAMPs on microbes recognised by Pathogen recognition receptors on phagocytes
How is pathogen recognition assisted?
Via opsonisation. Opsonins bind to microbial surfaces leading to enhanced attachment of phagocytes.
Give 3 examples of opsonins
IgG, CRP, C3b
What are the 2 main methods by which phagocytes kill microbes?
Oxygen dependent and oxygen independent
What is the complement system?
C1-C20 serum proteins that recruit phagocytes, opsonise pathogens and kill them
What are the 2 pathways by which the complement system can be activated?
o MBL pathway – initiated when MBL (produced by liver) binds to mannose containing residues on pathogen surfaces.
o Alternative pathway – Initiated when C3b is bound by cell surface microbial constituents.
