Immunology ABBAS & Integration Flashcards
A newly emerged virus is causing an epidemic in Africa. lnfected individuals usually die from the disease in less than 10 days with high amounts of viruses in their bodies. A small proportion of patients survived the disease and cleared the viruses. The sera from these recovered individuals could be used to treat infected individuals quite effectively.
For those patients who died from the acute disease (less than 10 days), what types of immune responses do you think have failed to protect them? Name these responses and explain their functions. (5 + 5 marks)
Innate Immunity
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Adaptive Immunity
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A newly emerged virus is causing an epidemic in Africa. lnfected individuals usually die from the disease in less than 10 days with high amounts of viruses in their bodies. A small proportion of patients survived the disease and cleared the viruses. The sera from these recovered individuals could be used to treat infected individuals quite effectively.
For those patients who died from the acute disease (less than 10 days), what types of immune responses do you think have failed to protect them? Name these responses and explain their functions. (5 + 5 marks)
Innate Immunity
Antimicrobial defences specific to each system – mucus production in the airways, which traps invading infective agents, and elimination of mucus by ciliary escalator; in the GIT, low pH in the gastric environment which destroys a large proporption of infective agents and commensals which confer competitive protection against infection.
Epithelial Barrier - the epithelial barrier, whether it be the respiratory airways, the gastrointestinal tract, or skin, serves as a physical and chemical barrier against entry of viruses and other microbes. Intraepithelial lymphocytes are responsible for eliminating microbes and infected cells. Note that antibiotics such as defensins are an important defense mechanism as well but it is directed more specifically towards bacteria.
Type I Interferons – Type I Interferons, which consist of both IF-α & IF-β released by infected cells, induce adjacent cells to transit into anti-viral states. Various signalling pathways are activated that inhibit viral replication and destory viral genomes.
Natural Killer (NK) Cells – NK cells function to eradicate reservoirs of infection and obligate intracellular microbes such as viruses by discharging cytoplasmic granules capable of inducing apoptosis in infected cells.
Pattern Recognition Receptors e.g. Toll-like receptors – these receptors recognize DAMPs and PAMPs, activating signalling pathways which (1) increases the expression of cytokines and other effectors of acute inflammation, and (2) increases the production of IF-1, converting more cells into an antiviral state.
Adaptive Immunity
Antibody production by plasma cells – Antibodies produced by plasma cells have multiple functions: (1) neutralization of virus, (2) activate complement, (3) antibody-dependent cellular cytotoxicity, which are all important mechanisms in combatting the viral infection.
Cytotoxic T cells – Cytotoxic T cells can kill infected cells with high specificity after recognizing viral antigens presented by MHC Class I molecules (and the costimulatory molecules). It is an important immune response in combatting and eliminating the viral infection.
Get the bolded words can alr, explaination you will know how to write from understanding the topic.
Antibody diversity is based upon?
Antibody diversity is based upon?
Combinatorial and junctional diversity
Briefly describe how we arrive at such a diverse range of Ag receptors?
Briefly describe how we arrive at such a diverse range of Ag receptors?
1) Combinatorial diversity: use of diff random combinations of V, D and J gene segments
2) Junctional diversity: inserting random nucleotide sequences introduced at joining sites between V, D and J gene fragments
Quite straightforward! its like grabbing a random V segment, random D segment, random J segment, mashing them together (thats already alot of possible permutations), then anyhow put nucleotide in between the joining sites (even more permutations)!!
Define affinity? Describe avidity
Define affinity? Describe avidity
Strength of binding between a FAB region of an AB and its target epitope
Strength of binding when several binding sites on an antibody bind simultaneously to a large antigen with multiple repeating epitopes
Describe briefly how selection of T cell during development works
How are the variable (V) regions of antibody genes formed?
How are the variable (V) regions of antibody genes formed?
By somatic recombination of ‘randomly’ selected gene fragments
Combinatorial diversity and junctional diversity!!
How many Fab and Fc does each IgE molecule have?
How many Fab and Fc does each IgE molecule have?
Fab: 2 identical portions binding Ag
Fc: 1 single region needed for the biologic activity and effector function of Ab
Is isotype switching reversible?
Is isotype switching reversible?
No
The development of adaptive immune response involves what of the gene fragment?
The development of adaptive immune response involves what of the gene fragment?
Somatic rearrangement of the gene fragments
What are some functions of Antibodies (Antigen receptors of B cells)?
What are some functions of Antibodies (Antigen receptors of B cells)?
- Membrane-bound Ag receptors
- Secreted proteins – present in blood and mucosal secretions
- Secreted Abs neutralise and eliminate microbes and toxins
- Secreted Abs are effector molecules of humoral immunity
- Immunoglobulins (Igs) – immunity-conferring proteins with characteristic electrophoretic mobility of plasma globulins
- Recognise microbial Ags by variable domains
- Constant region can bind to other molecules (receptors on phagocytes, complement proteins) which participate in eliminating Ags
What are the antigen receptors on B cells? What about T cells?
What are the antigen receptors on B cells? What about T cells?
Ag receptors
- B cells: membrane-bound Abs (BCR)
- T cells: TCR
What are the function of the V and C region of Antigen receptor?
What are the function of the V and C region of Antigen receptor?
Variable (V) region
- Region which recognises Ag
- Vary between clones of lymphocytes
- Variability determined by hypervariable regions/complementary –determining regions (CDRs)
Constant (C) region
- Conserved among all clones
- Important for structural integrity of receptor and effector funtions
What coordinate the joining of the random fragments?
What coordinate the joining of the random fragments?
RAG recombinase
What encourages a B cell to change to producing a specific isotype?
What encourages a B cell to change to producing a specific isotype?
‘switch factor’ cytokines that are produced by specific t helper cells subsets
IgE is IL4 from Th2
What happens to a B cell if it fails to express Pre-BCR?
What happens to a B cell if it fails to express Pre-BCR?
It will die
