Lecture 7: Innate immunity Flashcards
First line of defence:
Behavioural, societal, cultural
First lines of INDIVIDUALS defence?
skin and membranes
some epithelia are good barriers:
- hairy skin
- tight junctions
chemical individual defences
- Sweat, lactic acid, sebum, lysozymes
- Stomach pH
Defensins
- +ve peptides (15-20 residues)
- Broad spectrum
- -Microbes, viruses and parasites
- Target membrane
some epithelia are risky
-moist membranes: eye respiratory system GI system GU system (conjunctivitis, TB, syphilis)
Key players in immunity:
- The lymphatic and cardiovascular systems / cells (and others)
- Effector and signaling molecules
innate immunity:
- Physical barriers
- Phagocytes
- Immunological surveillance
- -Natural killer cells
- Interferons
- Complement
- Inflammation
pathogen recognition: no ‘recognition’
e.g. stomach acids, defensins
pathogen recognition: General recognition
pathogen-associated immunostimluants
- F-met- prokaryote proteins
- Lipopolyscaccharid (LPS)
- Foreing nucleic acids
pathogen recognition: Pattern-recognition receptors (PRRs)
- soluble (e.g. compliment system)
- Membrane-bound (e.g. toll-like receptors)
collectins:
- Soluble plasma components (+ surfactant)
- Bind to specific carbohydrates
- Bind to phagocytes
- Or (mannan-binding lectin) interact with complement
complement system
- 20+ soluble proteins, some are enzymes, PRR’s
- bring lysis, phagocytosis, inflammation
toll-like receptors:
- Macrophages, neutrophils, epithelia
- Bind range of pathogen proteins, inc. LPS
- Promote inflammation
interferons secreted by:
- Lymphocytes, macrophages etc
- Virus - infected cells
Secretion evoked by e.g. 2x stranded RNA
interferons inhibit viral replication by
-If alpha - attracts and increases NK cells
- If beta - slows inflammation,increases NK cells
If gamma - stimulates T-cells
immunological surveillance
- NAturla killer (NK) cells
- destroy bacteria, virus - infected & tumour cells
- target cells have low MHC I
Overall innate immunity:
- broad spectrum
- rapid
- no memory
- old
- requires cell-cell communication
- links to adaptive immunity
