NEUR3002 Immune brain Flashcards
What is the innate immune system?
The first line of defense, a subsystem of the overall immune system
What are the major functions of the innate immune system
Recruit immune cells to sites of infection,
activation of the complement cascade,
identification of foreign substances,
activation of the adaptive immune system
What are the newer functions of the innate immune system
- nervous system development
- refinement of neural circuits
- removal of dying cells during the neuronal cell death period
What is the complement cascade
A collection of proteins floating around in the blood that causes a series of (cascades) reactions to help remove pathogens such as the removal of bacteria by phagocytosis. This all happens before activation of the adaptive immune system.
It also recruits immune cells to the sites of infection or damage to induce inflammatory responses
What are the functions of the complement system
- Augments host defences
- recruitment of immune and inflammatory cells
- destruction of foreign organisms
- excessive complement activation links to numerous immuno-inflammatory diseases
- novel roles in central nervous system including, synaptic remodelling, neural degeneration
- ageing of the CNS
What are the functions of C1q and C3b
C1q and C3b are Opsonisins coaters. Foreign cells are tagged with complement C3b and C1q which are recognised by host receptors to induce phagocytosis.
Summary: C1q and C3b coat foreign cells to help host receptors (CR1) recognise them to be induced by phagocytosis
What are the functions of C3a and C5a
-C3a and C5a are come get me and come find me signals
- Potent inflammatory mediators
- help recruit inflammatory through the release of inflammatory cytokines
- they mediate most of these actions through binding to their cell surface
What are the receptors of C3a and C5a
C3a = C3aR
C5a = CD88 and C5L2
Both are G-protein coupled receptors. Their activation leads to up regulation of inflammatory cytokines as well as neuro-protective and neuro-degenerative effects
What are the find me signals
migration to the site, release agents from dying cells, followed by activation of proliferation
what else does complement do
Cell lysis = membrane attack complex
What roles do components of complement provide in developing CNS
- removal of dying neurons
- removal of excess synapses
What percentage of motor neurons die between E12 to birth
50%
What is the removal process of dying motor neurons
Microglia invade the CNS prior to development cell death. found around dying motoneurons and eat them by phagocytosis. Complement C1q and C3b are involved
What triggers the removal of nerve terminals
Opsonisation by C1q. C1q and C3b are present during the prunning of excessive synapses
How are synapses removed
C3b is deposited on the presynaptic terminal - weak, it is then opsonized, then CR3 is on the presynaptic terminal leading to microglia and recognition, resulting in phagocytosis
