Immune Flashcards
What are the three main benefits of the body as a habitat for potential pathogens?
Nutrient source
Good setting for growth and reproduction
A good vector for transmission
Name some potentially harmful organisms.
Viruses Bacteria Fungi Protozoa Helminths
What are the physical barriers of the body?
Skin - sheds old cells and bacteria
Dendritic (langerhan’s) cells present antigens
What are the main chemical defences of the body?
Anti microbial peptides Lysozyme Sebum Salt Tears contain lysosomes
Where are anti microbial peptides found, and what is their role?
In sweat, they interrupt cell growth.
Where are lysosomes found and what is their role?
Found in sweat and tears, breaks down cell walls.
What is the role of salt on the skin?
Creates an osmotic gradient for bacteria, drawing water out of the cell.
Where are mucosal membranes found?
Ocular, respiratory, oral and urogenital tracts
Briefly describe the muco-ciliary escalator
Goblet cells produce mucous, which traps microbes and duct, cilia beat in time and move mucous up the throat where it can then be swallowed or removed.
What is the role of micro flora?
They are better adapted to our bodies than bacteria and so they out compete them. Help us develop immunity and produce anti microbial peptides. They can cause opportunistic infections.
What are the features of the GI tract which protect against infection?
Low pH, toxic bile from gall bladder, digestive enzymes, mucus
What features of the urogenital tract helps prevent infection?
The osmotic gradient
Urine flow
Low pH
What do TLR’s distinguish between?
Self, harmless non self and harmful non self
How do TLR’s work, where are they found and give an example?
They recognise structures unique to microbes, are found on membranes of our immune system cells and an example is TLR - 5 which recognises flagellin.
What effects does TLR activation have?
Activation of the immune system, release of anti microbial peptides, and inflammation.
What is found in blood plasma?
Compliment proteins and antibodies.
Where are WBC’s produced?
In the bone marrow
What is the name for any blood cell which is not a lymphocyte?
Myeloid cells
What are the four types of granulocytes?
Neutrophils
Eosinophils
Basophils
Mast cells
What is the function of neutrophils?
Highly phagocytic
Most abundant leukocyte at 40 - 75%
Have a half life of 1-2 days
What is the function of eosinophils?
1-6% of WBS’s
Phagocytic and releases toxic granules
Mediates allergic reactions
What is the function of basophils?
Low number in blood 0.5% total WBC’s
No phagocytosis
Mediates allergic reactions and fights worm infection via granule release
What is the function of mast cells?
Line mucosal surfaces
Release granules which attract white blood cells
Describe the monocyte to macrophage transformation.
Monocytes have low phagocytic abilities. They then develop into macrophages which have high phagocytic abilities. They can either become sessile or migratory.
Describe dendritic cells.
Present in blood and all tissues in contact with the environment. They are phagocytic and good APC’s, triggering the acquired immune response.
What is the purpose of lymphatic vessels?
They drain ECF and lymph tissues, providing a site for immune system and antigen interaction.
What is the role of the spleen?
Filters blood antigens.
Where are different cells found in the lymph node?
APC’s present antigen to T(h) cells in the cortex
T cells influence B cells in the medulla.
What are the symptoms of inflammation?
Redness Swelling Loss of function Pain Heat
What occurs during inflammation?
Anti microbial peptides which interfere with microbial growth and reproduction.
Interferon is released from virally infected cells.
What do mast cells release when damaged or activated?
Histamine - Vasodilation
Prostaglandins - Vascular permeability
Leukotrines - “” “”
What functions does interferon have?
Infected cells undergo apoptosis
Uninfected cells destroy RNA and stop protein synthesis
Immune cells are activated
What are the side effects of interferon?
Muscle aches, chills, headache, fever
What are the three compliment pathways? Which one is fastest?
Classical fastest (antibody/antigen binds compliment)
Alternative (compliment binds to pathogen)
Lectin (Carbohydrate complexes of microbes bind to compliment)
What are the three main functions of complement?
Label/opsonisation coats microbe with antibody/C3b, making microbes more likely to be phagocytosed C3b
Recruitment attracts phagocytes to the area. Mast cells are degranulated. C3a and C5a
Destoy microbes, either via phagocytosis of C3b microbes or MAC complex assembly.
Breifly describe the inflammatory response
Cytokines released by mast cells and macrophages.
Fluid and leukocytes flow into the area
Phagocytosis occurs
Briefly describe a fever response.
Phagocytes release pyrogens (IL1)
This increases prostaglandin production in the hypothalamus.
This resets the set point for temperature to a higher value, hence fever
What compliment is opsonisation?
C3b
What compliment is recruitment?
C3a and C5a
Where do T cells mature?
Thymus
How is the unique TCR produced?
Through gene rearrangement from the germline state.
How are T(h) cells activated?
DC’s phagocytose and present antigen via MHC II
What are the two main roles of CD4+ cells?
Help cytotoxic cells become active Help B cells make antibody, activate Helps macrophages form phagolysosome in chronic CMR Help themselves activate All through the use of cytokines.
What do T(c) cells bind to?
MHC I
How are B cells activated?
By native antigen and CD4+ cells
Where do B cells develop?
Bone marrow
What do B cells produce once activated?
Plasma cells which produce antibody
Memory cells which don’t need T cell activation in subsequent infections
How many BCR on each B cell?
100,000
What is the order of isotope switching?
M/D to G to A to E
What are the three main antibody functions?
Opsonisation/agglutination
Complement activation
Neutralisation
Where is IgM found and what is its shape?
Pentameter, with a J chain
Found on naive B cells
What is the function of IgM?
First to resend after initial exposure
Good at activating compliment
Target extra cellular bacteria
BCR
Where is IgD found?
Naive B cells
What is the function of IgD?
Unknown
Where is IgG found, what is its structure?
Found in blood, is a monomer, the most prevalent in blood.
What is the function of IgG?
Opsonise/neutralise bacteria
Can cross placenta - passive immunity
Targets viruses and bacteria.
What is the structure of IgA? Where is it found?
Dimer, J chains
Found in secretions and mucus
Monomer in blood
What is the function of IgA?
Mucosal membrane defence
Passive immunity in breast milk
Targets viruses and bacteria
What is the structure of IgE? Where is it found?
A monomer, in blood.
What is the function of IgE?
Targets parasites
Allergic reactions
What’s a monoclonal antibody?
Antibodies derived from a specific B cell lineage.
What are the uses of monoclonal antibodies?
Medicinal, diagnostic and research.
Describe the humoral response
There is colonial selection when the B cell recognises antigen
B cell presents antigen to CD4 cell via MHC II
Cytokines release from CD4 triggers plasma and memory B cell formation
Memory B cells last for years and don’t need T cell activation
How long does the primary immune response take? What antibody is most prevalent?
7 to 14 days, IgM
How long does the secondary immune response take, and what antibody type is most prevalent? What type of cells does this require?
2-3 days, IgG, requires memory cells.
Describe the general antibody structure
Two heavy chains connected by two disulphide linkages in the base.
Two light chains are connected to one of the heavy chains each by a disulphide linkage.
Two variable regions are present on each end.
Describe the acute cell mediated response
Cytotoxic T cells release perforin and granzymes to stimulate apoptosis of virally infected cell.
Describe the chronic cell mediated response.
If bacteria prevent phagolysosome formation, interferon gamma from T helper cells activates macrophages to promote the fusion of phagosome and lysosome.
How are endogenous antigens expressed through MHC II?
APC’s phagocytise viral proteins which have leaked from infected cells or dead cells, then present them via MHC II
Wat is colonial selection?
The selective expansion of lymphocytes which react with a specific antigen
What do natural killer cells do?
Kill Timor cells with low levels of MHC I
What are examples of artificial and natural passive immunity?
Placental IgG and milk IgA
Serum injection for a snake bite for example
What are artificial and natural active immunity examples?
Active immunity is making immunity oneself, requires the production of memory cells to mount a secondary response
Natural is the disease process
Artificial is a live vaccine
What are examples of dead vaccines?
Toxoid, subunit and conjugate
What do live vaccines do?
Give a good IgA response and memory T cells
What do dead vaccines do?
Give a good IgG response, and IgM initially. Must be administered more than once and intramuscularly.
What is attenuation?
Removal of virulent gene for vaccination purposes.
What is recombinant vaccination?
Antigen code is isolated, and either:
Put into another cell which synthesises proteins (recombinant proteins)
Or a recombinant vector displays antigen on cell surface. (Recombinant Vector)
What is a plasmid vaccine?
Has only worked on mice so far, they take a bacterial plasmid and insert it into animal cell so it synthesises antigenic protein.
What are adjuvants?
Chemicals in vaccines which increase immune response via:
Increasing inflammation
Increasing macrophage response
Increasing APC’S interactions
What is an allergy?
An inappropriate response to an innocuous antigen.
What is the definition if an antigen?
Anything which has the potential to be recognised by the immune system.
What are natural killer cells?
Large granular cells
Help combat viral infections and cancers
Produce toxic molecules to destroy target cell, and cytokines to help other cells kill their target.
What is type one allergic response?
Immediate hypersensitivity.
Quick response, 30 min
IgE mediated, binds to mast cells and eosinophils
Causes degranulation and inflammation
What is type two allergic response?
Cytotoxic response
T(c) cells and complement
Effects circulation in joints and kidneys
What is type three allergic response?
Serum sickness
10-14 days post injection of antivenin
Presents as a skin rash
Leftover antivenin stimulates IgG production leading to complement activation.
What is type four allergic response, and give examples?
Takes 1-3 days to occur
Involves helper T cells and macrophages
Examples are diabetes, graves and lupus
How can allergies sort of be prevented?
Immunotherapy and immunisation
How can allergies be detected?
An intradermal injection of allergen and waiting for a wheal and flare, 20-30 minutes after injection.
How does an allergic reaction occur?
DC takes up antigen
Moves to lymph node
Immune pathway occurs.
What is the role of IgE in allergies?
Is produced on first exposure, binds to mast cells.
On further exposure, this triggers degranulation of mast cells.
What are some effects on the GI tract in an allergic response?
Diarrhoea
Vomiting
Increase in peristalsis
What are some effects on the airways in an allergic response?
Contraction
More mucus production
Congestion and blockage
What are some examples of type one allergic reaction?
Hay-fever (allergic rhinitis)
Asthma
Eczema/uticaria
Anaphylaxis
How high is the genetic predisposition to allergies in developed countries?
10% and rising.
Describe the events of phagocytosis
Pseudopodia surround microbe Microbes are engulfed Microbes ingested into phagosome Becomes phagolysosome Microbe killed and digested Microbe exocytosed
