12. Immunology Flashcards
List out the innate immunity cells:
- Macrophages
- Neutrophils
- Dendritic cells
- NK cells
- Mast cells, basophils, eosinophils
MNDNMBE
What are our adaptive immunity cells?
- B cells: antibody secretion
- IgM: pentamer, more prevalent in primary infection
- IgG: monomer, more prevalent in secondary infection
- IgA: dimer, bound to J chain (protect mucosal surfaces, e.g. saliva)
- IgE: monomer (mast cell degranulation => driver of asthma/allergies) - T cells
- CD4 T cells (helper): secrete cytokines => help B cells make Ab => coordinate antigen-specific adaptive response
- CD8 T cells (cytotoxic): kill infected cells via lysis, require perforin & gransyme
* T cells involved in BOTH cellular & humoral immunity (help B cells make Ab)
What do CD4 T cells recognise? (Antigen presentation)
EXOgenous antigens on MHC Class II
- exogenous antigens inhaled/ingested/secreted by microbes, then taken up by dendritic cells
What do CD8 T cells recognise? (Antigen presentation)
ENDOgenous antigens on MHC Class I
- endogenous antigens generated within cells
What does a cytotoxic T cell release to kill?
Releases perforin & granzyme
What cell presents antigens to immune cells of the body?
Dendritic cells
- presents antigens to T lymphocytes (APC)
Selective IgA deficiency most likely leads to
Sinusitis
Intravenous fluid contaminated by which substance found in bacterial cells can result in signs and symptoms of septic shock, even if no viable bacteria is found?
Lipopolysaccharide
- it induces pdn of prostaglandins => fever
Removal of which organ will cause an increased risk of infection by encapsulated bacteria like Strep Pneumoniae?
Spleen.
- cuz it fights any invading germs in blood
Which cell is cytotoxic and kills infected cells without the need for adaptive immunity response?
NK cells
- cytotoxic, induce apoptosis of virus-infected & tumour cells
What are antigens made of?
An antigen is just a molecule that can stimulate a response
- antigens are usually proteins
Immune system is not inherited from parents but..
Developed during the lifetime of an individual
What does CD number mean?
Cluster of Differentiation.
CD numbers are used to define cell types.
Name the secondary lymphoid organs:
- Lymph nodes
- Spleen
What are the targets recognised by dendritic cells?
Innate immunity targets:
1. PAMP: produced by pathogens, do not evolve rapidly, not shared w host
- pathogen associated molecular patterns
2. DAMP: host cell components released by damaged/stressed tissues
- damage associated molecular patterns
What happens if you remove the spleen?
Increased risk of infection by encapsulated bacteria like S. Pneumoniae
What are interferons, + specifically Type I interferon?
- type of cytokine, part of innate immune system
- released by infected cells early on during viral infection => increases resistance of neighbouring cells against infection
- inhibits viral replication
- IL-6 stimulates secretion of C reactive proteins
What are Lysozymes?
- powerful digestive enzymes that destroys the polysaccharides that coat the outer wall cell wall of bacteria
- secreted in tears and cells
- also a major enzyme component in egg whites, why eggs dont get infected.
What do TLR-4 on our dendritic cells and macrophages detect for?
Lipopolysaccharidse (LPS), thus, detecting presence of gram -ve bacteria
What do Neutrophils do?
- most abundant immune cell
- comes in first wave of leukocytes to enter infected sites via blood
- survives only 48hrs
- basically ur first responders to sites of infection
- kills microbes using similar mech as macrophages (phagocytosis + bactericidal mechs)
Which cell links the innate to the adaptive immune system?
Dendritic cell
How is the Innate immune system linked to the Adaptive immune system?
- Dendritic cell captures pathogenic/intruder material in tissues, processes the material (digests, smashes n displays itself w protein fragments)
- Then Dendritic cell migrates into regional lymph node via afferent lymphatics
- Specific lymphocyte (the one) in lymph nodes encounters dendritic cell displaying recognised pathogen peptide
- Formation of stable synapse => stimulates lymphocyte to proliferate & differentiate
What is the chronology of an immune response?
- Break in barrier defence => infiltration of microbes into site
- Detection of PAMP & DAMP via innate immune receptors
- Release of cytokines & chemokines by macrophages at site
- Infiltration of neutrophils from blood
- Migration of dendritic cells from infected site to local draining lymph nodes
- Initiation of adaptive immune response (B & T cells)
How do CD4 T cells (helper) react?
- secrete cytokines => help B cell make Ab => coordinate antigen-specific adaptive response
How do CD8 T cells (cytotoxic) react?
- kill infected cells via lysis, require perforin & granzyme
- it pokes holes in the cells n causes it to lyse and leak
How do antigens enter via the gut?
- Microfold cells
- uptake of antigens into gut via endocytosis
- antigens bind to dendritic cells in ‘pocket’ of Microfold cells => activation of T cells - Dendritic cells
- extend processes across epithelium => capture antigen on gut mucosa
- mucosa pathogens can enter via M/dendritic cells
Name the components of Gut Associated Lymphoid Tissue (GALT)
- Specialised antigen uptake e.g. microfold cells, dendritic cells
- Large no. of lymphocytes
- epithelium: mainly CD8 T cells
- lamina propria: mainly CD4 T cells - Peyer’s patches
- in small intestine
- rich in B cell folliclces, smaller T cell areas - Humoral immunity
- IgA>IgM>IgG (IgA prevents bacterial adhesion & directly inactivates virus)
What are the functions of antibodies?
- immune complex & agglutination => trap pathogens (IgM, IgG)
- complement activation by binding to target cells (IgM)
- opsonisation (coat pathogen in Ab) => enhance phagocytosis (IgG)
- neutralisation of bacteria/toxins/viruses, by blocking binding (IgG, IgA)
- Ab-dependent cellular cytotoxicity (ADCC)
- Mast cell degranulation (IgE)
A child has dengue 3 days ago, which immunoglobulin will be high?
IgM (response to new antigen)
What does the complement system do?
- aid phagocytes & Ab in killing pathogens
- activation: lysis, phagocytosis, opsonisation, clear immune complex (e.g. type III hypersensitivity) => NO stimulation of Ab pdn
The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) 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.
