Week 1 Study Questions Flashcards
Innate immunity cell mediators and its role
- Provides early defense against microbes, cellular and molecular mechanisms are in place before infection – does not involve antibodies
- NK cells, dendritic cells, neutrophils, phagocytes/macrophages, epithelial barriers, complement activation
Adaptive immunity cell mediators and its role
- Specific defense system & ability to respond more
vigorously to repeated exposures to the same microbe – memory - T cells, B cells, effector T cells, antibodies
Describe the cytokines involved in myelopoiesis and the differentiation pathway they control
Stem cells: secrete SCF, IL-6 and Flt3L to produce a common myeloid progenitor
Common myeloid progenitor:
- driven by IL-5 to become an eosinophil
- driven by G-CSF to become a neutrophil
- driven by Flt3L to become a macrophage
- driven by M-CSF to become a monocyte
What are M1 and M2 macrophages?
- M1 macrophages stimulate Th1 cells and are involved in a fight response against pathogens
- M2 macrophages stimulate Th2 cells and are involved in a healing response
Functions of M1 macrophages
- Involved in classical complement activation
- Anti-microbial and anti-tumour properties
- Pro-inflammatory, and secrete IL-6
Functions of M2 macrophages
- Involved in alternative complement function
- Wound healing and tumour growth properties
- Anti-inflammatory, and secrete IL-10
Name the different subsets of dendritic cells
- Classical DCs (cDCs)
- Plasmacytoid DCs (pDCs)
- Inflammatory DCs (infDCs)
- Langerhans cells (DCs of the skin)
How can NETosis contribute to disease?
- NETosis is the release of intracellular proteins potentially giving rise to auto-antigens and release of DAMPs that amplify ongoing immune reaction (e.g. MPO, ROS, TF)
- Lots of auto-antigens -> immune system doesn’t shut off or self-regulate -> excessive inflammation
- NETs can damage the host.
- NETosis has a role in variety of pathophysiological conditions (e.g. there are many NETs in the sputum of cystic fibrosis patients)
What are some of these diseases NETosis contributes to?
- Some diseases NETosis contributes to includes SLE, rheumatoid arthritis, cystic fibrosis, thrombosis etc.
Naïve CD4+ T cells can be polarised into different effector subsets –what are they and what do they do?
- T helper 1 (Th1): involved in driving cytotoxic CD8, secretes INFy
• Th2: involved in allergy responses and parasites, secretes IL-4
• Th17: maintain barrier immunity at mucosal surfaces, secretes IL-17
• regulatory T (Treg) cells: maintenance of immune cell homeostasis, regulate immune cell activites, secrete TGFB
Explain how Treg cells are critical for the maintenance of self-tolerance and immune homeostasis
- Treg cells suppress potentially harmful activities of several immune cells
- Treg cells are activated via the TCR to become suppressive
-Treg-cell activation is antigen-specific; and the suppressive activity of Treg cells is triggered in an
antigen-specific fashion
- Once they are activated, they do not require re-stimulation via the TCR to suppress and suppression is not MHC restricted
- Secrete TGF-β, IL-4 and IL-10 which contribute to
suppression
How do innate lymphoid cells differ from the various Th cell subsets?
- Innate lymphoid cells are bone derived
- Innate lymphoid cells do not express antigen receptors or undergo clonal expression
- ILCs are earlier in their immune response comparing to other T helper cells
Describe some of the ways ILCs assist an immune response and describe how they can also be involved in immunopathology.
-Macrophage activation, mucous production, vasodilation, thermoregulation, phagocytosis etc.
Describe the different roles of ILC2 and ILC3
ILC2: are involved in mucous production, alternative macrophage activation and vasodilation, some examples of cytokines released include IL-4 and IL-5
ILC3: involved in phagocytosis and epithelium survival, some examples of cytokines they secrete are IL-17 and IL-22
True/False: In hydrodynamic focussing, sheath pressure is greater than sample pressure
False: the sample pressure is greater than the sheath pressure otherwise both will mix together -> you will not see single cells
True/False: Flow cytometry can be used for bacterial analysis
True: make sure instruments are very clean because particle size can be similar to the debris of WBCs
True/False: Forward scatter measures granularity
False: forward scatter measures size, side scatter measures granularity
True/False: Cytokine bead array works on a similar principle as an ELISA
True
Explain the difference between a longpass filter and bandpass filter
Longpass: If filter is set to 500nm, then wavelengths of 500nm or more will pass through
Shortpass: If filter is set to 500nm, then wavelengths of 500nm or less will pass through
Bandpass: If filter is set to 500nm, then wavelengths of
+/- a certain amount will pass though (e.g. 500+/-50, then 475-525nm will pass through)
Describe how you would correct for spectral spillover
- Compensation by increasing the voltage values so that all the single stained cells
Neutrophil killing of bacteria by release of phagolysosome
- Neutrophils phagocytose microbes, which initiates the release of phagolysosome
- This is an enzyme that breaks the bacterial wall, and cationic peptides and ROS help to kill the bacteria
Neutrophil killing with NETS
- Neutrophils release their content to trap microbes and stop their spread
- NETS can include Neutrophil elastase (NE), cathepsin G, lysozyme, myeloperoxidase (MPO) and proteases
Ion chelators and histones - These can kill GP and GN bacteria, parasites and fungi
What are the differences between the effects of splenic and intestinal ILC3s
- Splenic ILC3s: increased CD40 & CD80/86 after IL-1β
stimulation and promote CD4+ Th cell responses - Intestinal ILC3s limit commensal bacteria specific
pro-inflammatory CD4+ Th cell responses →
maintain intestinal T cell tolerance
Classical DCs
- DCs are antigen presenting cells, activate naïve T cells, and link innate and adaptive immune responses
- Matured by Flt3L
- Classical DCs are found in blood, lymph nodes (LN), spleen, and non lymph tissues including skin, liver, lung & gut
Langerhans cells:
- Originate from precursors in the skin before birth (yolk sac progenitors & foetal
liver–derived monocytes). - In steady-state, LCs self-renew in situ independent of bone marrow (no replacement by bone marrow precursors) and development is independent of Flt3L.
- Express MHC-II and induce
differentiation of Th2 cells
Plasmacytoid DCs (pDCs)
- Circulate in the blood and lymph node compartments
- Secrete large amounts of Type I interferons in response to viral infections
- In steady-state – poor capacity to stimulate CD4+ T cells (low MHC Class II & costimulatory receptor expression and limited phagocytosis of antigens)
- When activated – dendritic morphology, up regulate HLA-DR & co-stimulatory
receptors, differentiate into functional APC and activate naïve CD4+ T cells
Inflammatory DCs (infDCs)
- DCs derived from monocytes in an inflammatory setting
- Recruited to sites of inflammation & produce TNFα and iNOS,
- Promote early pathogen specific T cell responses, preferentially induce Th1-type responses
- Initiate inflammation and support the function of cDCs
Classic DC positioning
- Strategically positioned at body barriers and organ entry points & migrate to T
cell zones within lymphoid organs or towards tissue-draining LNs → efficient stimulation of naïve T cells
Outcomes of T cell encounters with MHC-peptide on cDCs
- T cell proliferation
- Th cell polarisation (Induce differentiation of helper T cells)
- Memory cell formation
3 signals required from cDCs for T cell outcomes
- MHC-peptide – T cells interact with cell associated Ag
- Co-stimulatory signals (induced by microbes) – T cells respond to peptides from microbes and not harmless molecules
- Instructing cytokines – direct
polarisation
Antigen presentation and half life of cDCs:
- Short half life of ~ 3-6 days – constantly replenished from bone marrow precursors in a Flt3L-dependent manner
- Specialised Ag processing cells – efficiently present endogenous & exogenous Ag in both MHC-I & -II contexts.
- Cross presentation (present acquired exogenous antigens on MHC class I to naïve CD8+ T-cells – ingested antigens transported from vesicles to cytosol where peptides enter the class I pathway
