Innate and adaptive immunity Flashcards
Describe the differences between innate and adaptive immunity
Innate immunity
- Non-specific
- Fast
Adaptive (a.k.a. acquired) immunity
- Specific
- Slow response (esp. 1st time)
What is the complement system?
- 30 plasma proteins that circulate in the blood as inactive precursors
- They are activated in response to infection, causing a cascade reaction –> enables rapid amplification of activated process
- Complement cascades link the innate and adaptive immune responses
(Conceptually not dissimilar to the clotting cascade)
Natural Killer cell
- Type of cytotoxic lymphocyte critical to the innate immune system
- Have the ability to recognise stressed cells without needing to be primed to an antigen like cytotoxic T cells, enabling a faster response
- Do not require activation to kill cells missing self-markers of MHC Class I
Opsonisation
coating of the surface area leading to increased phagocytosis
Describe the types of complement system (ak.a. the pathways)
3 types
- Classical pathway
- Antibody dependent
- Links innate and adaptive immune responses
- Effect of complement strongly amplified in the presence of an adaptive immune response
- Alternative pathway
- Interacts directly with the pathogen surface
- Lectin pathway
- Opsonises the pathogen
What do all the different complement pathways interact with? What does this do?
C3 convertase
Clinical relevance of C3
Canine C3 deficiency
- Inherited disorder in dogs that causes increased susceptibility to infection
- Homozygote dogs have no serum C3
- Therefore have difficulty making antibodies so suffer increased pyometra, pneumonia, sepsis etc.
Also Porcine Factor H Deficiency
- Factor H stops C3b activation
- This leads to accummulation of C3 on the kidneys etc.
- Carriers are born normal but show problems after a few weeks and die of anaemia and renal failure
Outline the membrane attack complex
- Mechanism that directly acts and kills bacteria
- Endpoint of all 3 complement pathways
- a.k.a. Terminal complement complex (TCC)
- Composed of C5b, C6, C7, C8 and multiple C9
- Forms pore in bacterial cell membrane, leading to dramatic loss of cellular homeostasis and allowing host lysozymes to penetrate bacteria
Immunological memory
exposure of an immunologically primed animal to the same antigen, leading to the activation of memory cells, which were established during the primary immune response. An enhanced immune response is the outcome.
Immunological memory is essential for the immune response to become more efficient upon reinfection of the same pathogen.
Antigen
substance which induces an immune response in the body.
Epitope
part of the antigen to which the antibody binds.
What can adaptive immunity be subdivided into?
Cell-mediated and humoral immunity.
Describe the events that lead to immunological memory
- Pathogen/antigen invasion
- Antigen capture and processing
- Antigen recognition
- Selection of lymphocytes specific for that antigen
- Cell activation
- Proliferation of antigen-specific lymphocytes to form a clone
- Differentiation into functional state (either effector or memory cells)
- When the pathogen is overcome, effector cells undergo apoptosis but memory cells ciruclate in blood/lymph body tissues for months to years
- If reinfected, there is an anamnestic response, which is much more efficient and has a greater amplitude than primary immune response.
True/False: the type of antibody produced can change between the primary and secondary immune responses
True
- The antiboy may become increasingly specific
- IgM predominates in the primary response and IgG in the later memory response
- NB: there isn’t really a clear cut primary and secondary response; it’s a gradient, with antibodies becoming more and more specific each time
All T cells are ____+
CD3+
