1 Introduction To Immunology Flashcards
*Q: What is the purpose of the immune system? What does it also detect? What type of process is this?
A: The environment is full of microorganisms - the immune system is a complex cellular and protein network that has evolved to protect the host from pathogenic microbes.
Tissue damage is also recognised by cells of the immune system-> type of HOMEOSTASIS
Q: What does the failure of the immune system lead to? (2) When the regulation of the immune system becomes unbalanced, what can it lead to? (2)
A: increased susceptibility to infection and sometimes cancer.
autoimmune disease and allergy.
Q: What is the normal function of the immune system? What enables it to do this? (2) What’s more important?
A: Identify and eliminate harmful microorganisms and harmful substances such as toxins:
By distinguishing self from non-self proteins
AND
By identifying danger signals (eg inflammatory signals)
you need both to trigger an immune response
Q: What reproduces faster, virus or bacteria?
A: Bacteria
*Q: Describe the evolutionary arms race between pathogen and host. (3)
A: The pathogen exerts selection on the host and the host exerts selection on the pathogen.
The pathogen reproduces much faster than the host and hence can evolve faster.
Therefore, the host relies on a flexible and rapid immune response.
Q: Which human genes are involved in the immune system? (2) How have they been selected?
A: Our most polymorphic genes - HLA, KIR- this variation has been selected for by exposure of populations to infectious disease.
*Q: What is the initial immune response called? Summarise the time-course of a primary immune response to a virus with a diagram. (3 lines) Explain the role of 3 cells involved.
A: The initial response is the innate immune response.
Early peak of type 1 interferon (interferes with the replication of the virus)
Peak in NK cells (can recognise infected cells and lyse them)
These responses help to flatten out virus replication.
To eliminate the virus you need more specific immune responses from the adaptive immune system - this takes a little more time.
Rise in Cytotoxic T Lymphocytes (recognise and lyse infected cells)
CTLs start producing antibodies against the virus
Graph: days after viral infection against magnitude of response with lines for: type 1 interferon (alpha and beta)= peak day 2, natural killer (NK) cells= peak day 4, cytotoxic T lymphocytes (CTLs)=plateaus day 7/8, antibody, (virus titer)
*Q: What is the primary response?
A: the first time the host has seen this particular virus
*Q: Describe the innate immune response. When is it present from? What does it rely on? When the infection occurs, are the components ready? What’s the range for specificity? Which type of molecular patterns does it recognise?
A: Present from birth
Relies on pre-formed and rapidly synthesised components
If an infection happens, the components are already there to deal with it.
Limited specificity (non antigen specific)
Only recognises molecular patterns to do with danger (non self)
*Q: Describe the acquired/adapted immune response. When is it acquired? What does it depend on? Is it specific or non specific?
A: Acquired after exposure to the pathogen- Gives immunological memory
Depends on CLONAL SELECTION
Slow - takes days
Antigen Specific
*Q: What is clonal selection? What is clonal expansion?
A: selection of appropriate lymphocyte to fight the pathogen
expansion of the clone of lymphocytes which recognises the particular pathogen
Q: What are examples of anatomical barriers for innate immunity? (3)
A: Skin
Mucus - trapping microbes
Cilial propulsion on epithelia
Q: What are examples of physiological barriers for innate immunity? (5)
A: Low pH
Secretion of lysozyme
Interferons
Anti-microbial peptides
complement
Q: When do antibodies develop?
A: don’t develop until you’ve been exposed to the pathogen so it’s totally part of acquired immunity
Q: What triggers the innate immune response? 2 types?
Examples? (2,3) Receptors? (1,3)
A: Pathogens have various molecular structures which aren’t present on normal cells - the immune system can take advantage of these differences and respond to these patterns.
-Pathogen Associated Molecular Patterns PAMPs (E.g. dsRNA in cytoplasm, bacterial cell wall components) ->
Pattern-recognition Receptor = TLRs (Toll-like receptors)
-Danger Associated Molecular Patterns DAMPs (E.g. Monosodium urate, high extracellular [ATP], reactive oxygen species) -> Pattern-recognition Receptors = NLRs - NOD-like receptors, RLRs - RIG-I-like receptors, AIM2
Q: Why is high extracellular [ATP] a sign of danger?
A: because ATP isn’t useful outside cells.
Q: What does the innate immune response do? (2) Main consequences? (3)
A: Destroys invading nucleic acids (e.g. viruses) in the cytoplasm
Activates interleukins which, in turn, activate inflammatory pathways
Evokes type 1 interferons - bind to receptors on nearby cells and induces an antiviral state.
Main consequences: Suppresses pathogen replication, buys time, kick starts the acquired immune response
Q: What is the acute phase inflammatory response? What does it involve? (2) What triggers 1?
A: innate response to tissue damage
Fever - indicative of acute phase inflammatory response (This is triggered by activation of interleukin-1)
Followed by production of acute phase proteins
Q: What are acute phase proteins? What are 3 acute phase proteins? Where are they produced?
A: soluble pattern recognition receptors
C-reactive protein, Serum amyloid protein, Mannan-binding lectin
liver
Q: What do the acute phase proteins do? Describe each one. What happens following binding? (2)
A: C-reactive protein and serum amyloid protein - bind to molecules found on the cell wall of some bacteria and fungi.
Mannan-binding lectin - binds to mannose sugar molecules which are not often found in mammalian cells.
Once these proteins are bound, phagocytes have receptors which can recognise these proteins and proceed to ingest the infectious agent.
binding can also trigger responses - it helps activate the complement system
Q: Describe cytokines. (2) What causes a cell to produce them?
A: Large family of soluble molecules - they are proteins that transmit information between cells
Some sort of stimulus
Q: How do cytokines act? (4) Important for?
A: diffuse to nearby cells, bind to specific receptors and send a signal to the cell to alter the pathogen gene expression. Proteins will either be upregulated or downregulated leading to the biological effect
proliferation of lymphocytes
Q: 3 examples of granular leukocytes?
A: Natural Killer (NK) Cells, Macrophages, Granulocytes (3 types)
Q: What are natural killer (NK) cells? What do they do?
A: Type of cytotoxic lymphocyte
Identify and kill virus-infected cells and tumour cells
Q: What are macrophages? What do they do?
A: Mononuclear phagocytes, Release cytokines as signals of danger
