Immunology & Inflammation Flashcards
What is the definition of immunity?
Protection from disease, especially infectious diseases, harmful/aberrant molecules and noxious/useful molecules.
What are the 3 primary levels of defence against infectious agents?
- Barriers
- Innate immunity
- Adaptive immunity
a. How do barriers work?
b. How quick do they work?
c. Give some examples.
a. Provide mechanical + chemical protection.
b. Immediately effective
c. Skin, stomach acid
What is different about adaptive immunity compared to barriers + innate immunity? What is the advantage of this?
Adaptive can deal with microorganisms that the body has not yet encountered as they work in a more highly specific way.
This means that if anew microorganism mounts with an adaptive immune response, then we are protected if we encounter it again.
Why don’t phagocytes attack RBCs?
Immune system can differentiate self from non-self ⇒ can recognise pathogen + non-pathogens = does NOT attack
What are 3 features of the immune system?
- Can recognise pathogens and differentiate them from ‘non-self’
- Has a mechanism of killing/eliminating pathogens
- Has a method of coordinating activities of different components of the system → uses signalling molecules (cytokines) = low MW proteins that are used in cellular growth + differentiation, inflammation and repair.
What is the role of lymphatic system in infection? Why does this happen?
The lymphatic system helps move lymphocytes around the body + help their recirculation around the body.
This occurs until we are infected, then they’ll migrate to the site of infection.
The lymphatic system then drains into the bloodstream either through the THORACIC or RIGHT lymphatic duct.
There is a constant flow of lymphocytes from blood → tissues, tissues → lymph + back to blood.
At the site of infection, there is an enhanced attraction to the site through adhesion molecules on lymphocytes, blood cells + chemokines.
What is innate immunity?
Immunity present at birth
What are 3 types of innate immunity?
Physico/biochemical
Humoral
Cellular
Give ONE example of a physicochemical factor
Mechanical barriers (e.g. keratinised epithelium of the skin)
Give ONE example of a biochemical factor
Secretion of antimicrobial substances like lysosome (hydrolyses peptidoglycan)
What is inflammation?
Body’s response to tissue damage which may have occurred from physical damage or infection.
How does the innate system respond to inflammation? (4 ways)
- Complements activation
- Attraction + activation of phagocytotic cells to the site of infection that release cytokines + chemokines
- Activates natural killer cells
- Altering vascular permeability – gets fluid to the site of infection (= swelling, vasodilation)
- ↑ Body temp
What is the ‘complement system’?
Part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen’s cell membrane.
What are the 4 roles of complement in inflammation?
- Gives rise to chemotaxis (= process of attracting using signalling molecules) of phagocytes (e.g. macrophages)
- Activates mast cells (WBC active in allergy + inflammation)
- Opsonisation and lysis of pathogens
- Clearance of immune complexes
What is the function of the complement system?
They are a cascade of reactions that lead to lysis of a microorganism.
What is needed to start the complement cascade?
Recognition of antibodies using a recognition molecule (such as C1q)
What is the role of C1q?
It binds to antibodies to cause a conformational change which then activates serine protease activity in the molecule
What are 3 ways that C3 can be cleaved?
- Cell lysis
- Solubilisation + removal of antigen-antibody complexes
- Production of pro-inflammatory conditions
What are the 3 complement pathways called?
Classical, alternative and lectin
What activated the classicial pathway?
Antibodies
How does the classicial pathway work?
- Reactions between antibodies + antigens activate the C1 component.
- C1 cleaves C4 into C4a + C4b
- C1 combines with C4b to make C14b
- C14b cleaves C2 into C2a + C2b.
- C4b + C2a combine to make C4b2b = C3 convertase
What is MBL?
MBL = C1q analogue that recognises sugar patterns unique to pathogens and those hidden on exposed healthy cells.
Where is MBL found in nature?
Cell walls of bacteria + fungi like salmonella, candida and neisseria
What activates the lectin pathway?
Binding of MBL
How does the lectin pathway work?
- MBL recognises when mannose enters the body via bacteria + fungi.
- Recognition activates MASP (= MBL associated serine proteases)
- MASP triggers activation of C4 and C2 and cleaves them into C4a + C4b and C2a + C2b.
- C2a + C4b combine to form C4b2a = C3 convertase
What activated the alternative pathway?
Certain substances (such as bacterial endotoxins) on pathogenic surfaces
How does the alternative pathway work?
- Spontaneous hydrolysis of C3 converts it into C3b
- This allows Factor B to attach to C3
- This opens the active site of Factor B
- Factor D cleaves Factor B into Ba + Bb
- C3b + Bb combine to form C3bBb = C3 convertase
What is the role of the Membrane Attack Complex (MAC)?
It forms channels within bacterial membranes that cause cell lysis of Gram-negative cells.
How is MAC made?
When C3 is cleaved, it makes C3b → this leads to C5 formation.
When C5b fragments are made, this will turn into MAC when combined with other products of the complement cascade.
What will happen if MAC forms on host cells?
Cell lysis
Why is CD59 important?
It prevents the insertion of C9 (+pore forming agent).
If cells lack CD59, they are more prone to lysis and can cause haemolytic conditions.
What are 4 times of complement activation?
- Cell lysis
- Opsonisation
- Cell recruitment
- Removal of immune complexes.
2 types of immunisation
Passive & active
What is passive immunisation?
Protective immunity WITHOUT the need for an immune response by the individual
What are 4 ways to get passive immunity?
- Newborn from mother
- Maternally derived IgG passively transferred through placenta
- IgA secreted in breast milk
- Administered immune globulins from humans who have recovered from the disease or have immunisation already
What is active immunisation?
When a non-immune individual has long-lasting protection against an infective organism by being able to create an effective immune response against the organism/toxic products
What is the main aim of active immunisation?
Development of immunological memory, so the immune system “remembers” how to fight off the specific pathogen, providing long-lasting protection
What is a vaccine?
Medicine used to induce active immunity
What is a live attenuated vaccine? How quickly can immunity develop from it?
Vaccine containing a weakened form of the live organisms with virulence factors removed.
Immunity is developed ~ 2 weeks after administration.
What is a killed vaccine?
Contains a NON-INFECTIOUS virus or bacterium as it does not have live, replicating microorganisms. Instead, the pathogens are inactivated or killed using physical or chemical methods while preserving their ability to stimulate an immune response.
Why would some vaccines need an adjuvent?
- Increase immunogenicity
- Prolong antigen at injection site for a slower release
Why can’t we always use attenuated vaccines?
Attenuation is only applicable to viruses that are easily + readily inactivated.
[RNA viruses are easier (than DNA) to attenuate because RNA is more likely to inactivate]
What is a subunit vaccine? What is the aim of using them?
Vccine that contains has a fragment of the pathogen (not the whole microorganism).
These vaccines are designed to stimulate an immune response against specific components (subunits) of the pathogen that are known to be immunogenic and capable of eliciting protective immunity.
What is needed to make a subunit vaccine?
Knowledge of viral structure + immune responses.
