Heaphy 9 Immunity Flashcards
Why do we need an immune system?
We are a niche, food source, environment, to be consumed and exploited by the microbial world. Immune system prevents this. Severe immune deficiencies not compatible with healthy life.
neonates:
some antibodies from breast milk, possibility even stem cells that can be detected in adult. underdeveloped immune system
Students:
immune system is good,
old:
failing immune system, lack of stem cells
Innate immunity:
- A more specific response with memory characteristics is also desirable
- Quick (bacteria replicate in hours) – days, weeks
Adaptive immunity:
- Slow, takes over to get rid of infection.
- Has “memory” to respond more quickly in days rather than months if been infected before.
- Blood borne: B lymphocytes => antibodies , T lymphocytes => effector cells
- Specific
Innate immunity:
Components:
• Non-specific, innate, host defences: no memory general barriers to infection e.g.
- Skin=> epithelial cells, Mucus with anitbodies etc
- phagocytes: eat bacteria,
- dendritic cells: recognize, chop & present to other cells to create an immune response
- NK cells: complement
Body secretions and fluids => variety of macromolecules to prevent e.g.
- Lysozyme: weakens end bacterial cell wal lactoferrin=> mops up free Fe to prevent bacteria getting it, Iron: not readily available, not soluble, bacteria have to secrete macro molecules to solubilise it
- cationic amphiphilic (a-helix, 1 base is +/ve charge other face is -/ve lyses bacterial cells as disruptive.)
‘defensin’ peptides,
- Fever: pathogens can grow at 37.4’C, killed if temp raised.
PAMPS :
pathogen associated molecular pattern.
Lipopolysaccharides, peptidoglycan, techoic acid, dsRNA (often in virus replication) unmethylated CpG
=> all recognised as foreign by adaptive immune system & primes for defence.
Interferons (alpha)
⇨ created when signals of RNA virus found.
• Proteins made which act to prevent virus replication in a variety of ways
• Prevents viruses from replicating => Switches on genes that code for proteins
• Extracellular signals => signal transduction pathway=> binds to cell surface, kinases => phosphorylated, recruit other kinases cycle => transcription factors => bind to DNA to switch on genes.
Natural killer cells
- Pathogen Infected cell results in down regulation of MHC1 (major histiopahto.. compatability), activation of NK cell => release of lytic chemicals that kill cell
- If MHC class not presented then kills it. Common of infection to reduce MHC
Major immune cell types, white blood cells:
- Neutrophils
- Monocytes/ Macrophages from blood/ body cells
- Dendritic cells
- Basophils
- Mast cells
- Eosinophils
- Lymphocytes
Neutrophils:
⇨ Most common WBC
⇨ If raised = chronic bacterial infection.
• Engulf bacteria- phagocytosis & Kill them
• Most common white blood cell
• Increase during infection and indicative of bacterial infection
• Also called granulocytes
• Recruited very quickly in infection
Monocytes/macrophages/dendritic cells
• M’s are Phagocytic => kill bacteria
• Dendtiric present them to immune system to create adaptive immune syste
Also involved in
• Maturation of an adaptive immune response
Basophils/Mast cells/Eosinophils
- Mast cells release histamine, increase lymph flow, recruit immune cells. Atopy, allergy response
- Eosinophils, kill parasites
- Basophils?
ADAPTIVE IMMUNE SYSTEM
Lymphocytes:
mostly inactive (NKs are a type of lymphocyte)
• Classes:
- Naïve (never had pathogen to respond to),
- effector (recognised & responded & kill cells & most die)
- memory types (few survive for response next time)
