Immunology- An introduction to the immune system Flashcards
The immune system is a network of specialised cells, tissues and soluble factors that co-operate to kill and eliminate what?
Infections and diseases
How does the immune system fight infections and diseases?
- By distinguishing ‘self’ molecules from ‘non-self’ molecules
- By identifying ‘danger’ signals (e.g from acute inflammation) or via combination of the two
What are immune-suppresive and anti-inflammatory drugs essential for?
- Essential for thetreatment of autoimmune diseases, allergic diseases, asthma and cancer
- Key to preventing the rejection of donor tissues in transplant recipients
What are the two types of immunity?
Innate
Adaptive
What is innate immunity
Is present from continuously, it is a defense mechanism that is present from birth and is generally non-specific 9i.e the same generic response occurs towards many different types of material)
- First line of defence
- No memory
What is adaptive immunity?
Is induced by the presence of ‘foreign’ or ‘non-self’ material. the response that occurs is usually unique to the specific substance or pathogen that induced the response
What do both innate and adaptive immunity work closely together to do?
To eliminate disease-causing micro-organisms
What are the points of entry for innate immunity?
- Digestive system
- Respiratory system
- Urogenital system
- Skin damage
What are the routes of attack for the innate immunity?
- Circulatory system
- Lymphatic system
For innate immunity what are the protective physical and chemical mechanisms?
- Outer surface which is tough and impermeable to micro-organisms
- Inner surface bathed in moving mucous and acid secretions
- Commensal organisms
- Anti-microbial peptides
Specialised cells and molecules of innate immune response. How do phagocytic cells do this?
- Orchestrate initiation of response
- Recognise, ingest and kill bacteria and yeasts
Specialised cells and molecules of innate immune response. How do degranulating cells do this?
- Orchestrate initiation of response
- Damage and kill multicellular parasites and viruses
Specialised cells and molecules of innate immune response. How do secreted proteins do this?
- Complement (induced)
- Chemokines
- Cytokines
What happens in the first stage of infection?
Physical (natural) barriers breached, pathogens invade, innate immune responses initiated
What happens in the second stage of infection?
Tissue-resident innate immune cells recognise pathogens as ‘non-self’ and dangerous
What happens in the third stage of infection?
Macrophages ingest invading extracellular bacteria
What happens in the fourth stage of infection?
Mast cells step in and degranulation occurs where there is a release of pre-formed pro-inflammatory substances (e.g histamine)
Then gene expression occurs where there is a production of new pro-inflammatory substances
What are some examples of pro-inflammatory mediators?
Nitric oxide
- Prostaglandins
- Histamines
- Pro-inflammatory cytokines
In the 5th step of infection it is described at late innate response and acute inflammation occurs? How does this happen?
note- Its a positive feedback pathway
- Bacteria trigger macrophages to release cytokines and chemokines
- Vasodilation and increased vascular permeability cause redness, heat and swelling
- Inflammatory cells migrate into tissue, releasing inflammatory mediators that cause pain
What does the term oponisation mean?
The coating of pathogens by humoral (soluble) factors
What is C3a?
It is an anaphylatoxin which promotes acute inflammatory reactions
What does inflammation promote?
- Vascular changes
- Recruitment and activation of neutrophils (trans endothelial migration)
- Bacteria produce chemicals that attract neutrophils to site of infection
The process of trans endothelial migration can be divided up into a number of broad steps. What re these steps?
Weak binding ‘rolling’
Strong binding
Stable adhesion and aggregation
Transendothelial migration
What does the neutrophil killing mechanisms induce?
Phagocytosis
Degranulation
NETs
What is NETs?
Activated neutrophils release intracellular structure (NETs) into the extracellular environment
NETs serve to immobilise pathogens:
-Prevcents them from spreading
-Facilitates their phagocytosis
For intracellular pathogens i.e viruses, virally infected cells produce and release cytokines called what?
Interferons
What can Natural-Killer (NK) cells do?
Recognise and destroy virally-infected cells (and cancer cells)
They ignore normal healthy tissues and cells
How long does innate immunity intermediate take to act?
0-4 hours
How long does early induced innate response take to act?
4-96 hours
