Infection and Immunity - 4

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  • Created by: LBCW0502
  • Created on: 22-11-19 09:59
The innate immune response is found in which organisms
All organisms (even in bacteria - with restrictive enzymes)
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Why is the adaptive immune response used? (1)
Innate immune response may not be strong enough despite being amplified. Adaptive response allows the further amplification of innate immunity. Also organisms can evolve to resist innate immune response
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Why is the adaptive immune response used? (2)
Adaptive immunity allows an immune response to organisms which have overcome innate immunity (amplification of innate immunity) - organisms can stop complement pathway, resist phagocyte killing, evade/breach innate immunity (prevent humoral factors)
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The humoral component of adaptive immunity involves which soluble protein?
Antibodies (link between innate and adaptive immunity) - variable adaptor molecule (signal to know when innate immunity has been compromised
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Describe features of the antibody
One part has to detect micro-organisms (non-self) present, variable antigen binding site (recognises non-self, binds to micro-organism), other part of antibody (constant - activates classical complement pathway, Fc receptor on phagocyte)
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The innate immune response activates which complement pathway?
Alternative
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The adaptive immune response activates which complement pathway?
Classical
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How does the antibody join humoral factors and cell-mediated responses?
The antibody combines the micro-organism and phagocytic cell. Link between innate and adaptive immunity
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Variable binding sites on the antibody can change depending on what?
The micro-organism. Can turn on immune response (either classical pathway or binding to phagocytic cell)
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What stimulates phagocytosis?
Antibody bound to Fc receptor on phagocyte (bacterium can no longer avoid phagocytosis due to being bound to the antibody)
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What is an antigen?
Antibody generator (any primary sequence that can cause antibodies to be produced). Antigens can be complex (may require several antibodies in different parts of the primary sequence - epitopes)
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Describe the specificity of antibodies
Antibodies are specific for certain amino acid sequences (specificity - adaptive immunity). Antibody will bind to one antigen (one amino acid/primary sequence). Antigen and epitope are used interchangeably (but antibody binds to epitope/specific)
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What is the primary immune response?
Time taken for the immune system to recognise that there is a non-self, cell-mediate components of immune system produce antibody (turned on in the presence of the micro-organism)
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What is the secondary immune response?
Immune cells rest and become memory cells - found in secondary lymphoid tissue (faster production of antibodies). Adaptive immunity - memory to micro-organism encountered
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Describe features of immune cells and antibodies after birth (1)
After birth - developed all immune cells which have produced all the antibodies possible (for any possible epitopes). Small amounts of cells capable of producing antibodies
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Describe features of immune cells and antibodies after birth (2)
Born with population of B cells which produce all antibodies needed (with specificity)
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Why are antibodies not produced all the time? (1)
Not metabolically efficient. Also due to tolerance. Could possibly have blurred distinction where the immune system recognises self as non-self (certain mount of amino acid sequences)
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Why are antibodies not produced all the time? (2)
Antibody-epitope interaction (protein interactions). Could have same function and different amino acid sequence (extent?). Autoimmune disease - amino acid sequence so similar to non-self
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Why are antibodies not produced all the time? (3)
Immune system can't distinguish between this e.g. rheumatic heart disease
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The concept of vaccinations is based on which responses?
The primary and secondary responses (acquired, specific immunity)
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Antibodies are also known by which terms?
IgE or Ab
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What is the most common protein component in serum?
Albumin (followed by gamma globulins - IgG, IgA)
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What is the most common antibody in human serum?
IgG
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Describe the basic chain structure of the antibody (1)
4 polypeptide chains (heterodimers), heavy chain and light chains (named due to appearance after electrophoresis, size), chains linked by disulphide bridges, from N-terminus to C-terminus, can further divide protein on either side of disulphide bonds
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Describe the basic chain structure of the antibody (2)
Papain – Fab regions (antigen binding fragment, N-terminus – region which finds to epitope/antigen/micro-organism)
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Describe the basic chain structure of the antibody (3)
Fc region – first crystallised region – binds to phagocytic Fc receptor (communication between innate and adaptive system), activates classical complement pathway
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Describe the basic chain structure of the antibody (4)
Specificity (amino acids on N-terminus of antibody are variable/different). Constant region (amino acid sequence remains the same, to activate complement pathway, same function regardless of any antigen the antibody binds to). IgG1 - variable loop
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Describe features of other classes of antibodies (1)
Structural variation unrelated to antibody specificity. Different antibody structures (e.g. different disulphide bond in IgA). Usually produce IgM in immune response
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Describe features of other classes of antibodies (2)
Low concentrations but more antigen binding sites/10, able to fight infection with low antibody number. Low B cell number, low antibody production, want highest number of variable binding sites possible
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Describe features of other classes of antibodies (3)
Can switch between classes of antibodies but antigen binding site remains specific. B cell has specificity for given antibody but can switch between classes (depending on primary/secondary response)
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Which part of the antibody is responsible for binding the antibody to the epitope?
Idiotype (hypervariable, Ag combining site)
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State features of generating antibody specificity (1)
Light chain and heavy chain - 2 polypeptides to be made. Variable amino acids, constant amino acids. Gene fragments mixed in different orientations to give hybrid gene which can be transcribed, transcription can undergo normal processing
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State features of generating antibody specificity (2)
Splicing and recombination - gives variability. Somatic cells undergo mutation and variation in mRNA splicing
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Describe features of the classical complement pathway which is activated by human IgG1 and IgM (1)
Activation of classical complement pathway due to antibodies. C3 and antibody opsonise micro-organism surface. C1 protein binds to antibody in C-terminal region, other proteins (C4/2) also bound, C3 convertase formed (converts C3 to C3a and C3)
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Describe features of the classical complement pathway which is activated by human IgG1 and IgM (2)
C3a still have the same function (mast cell degranulation, chemoattractant)
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Describe the next steps in the classical complement pathway (activated by antibodies) in the presence of Gram-negative bacteria
C5 convertase formed (converts C5 into C5a and C5). C5a still has the same function (same as C3a)
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What is the difference between the classical and alternative complement pathways?
Classical pathway caused by antibody opsonisation. Alternative caused by C3b. Proteins which form C3 convertase is different in each of the pathways
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Describe features of opsonisation with antibody (1)
Method of coating organism. Increases adherence for phagocytes (combinations - increase chances of immune system recognising non-self e.g. IgM + C3, IgG + C3)
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Describe features of opsonisation with antibody (2)
Low number of antibodies produced due to tolerance, only produced in response to non-self, require innate response (phagocytosis), likely to produce better antibody response
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Summarise the antibody defences against bacterial infection (1)
Attachment (antibody to fimbrae lipoteichoic acids and some capsules), proliferation of organisms (block metabolic transport mechanisms e.g. receptor for Fe chelating compounds, trigger complement through Gram-negative outer lipid bilayers)
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Summarise the antibody defences against bacterial infection (2)
Avoidance of phagocytosis (neutralise immunorepellents, antibody to M proteins and capsules, opsonisation via Fc/C3 receptors). Damage to host (toxic - antibody to toxins, neutralisation, invasive - neutralise spreading factors e.g. hyaluronidase)
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Why is the adaptive immune response used? (1)

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Innate immune response may not be strong enough despite being amplified. Adaptive response allows the further amplification of innate immunity. Also organisms can evolve to resist innate immune response

Card 3

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Why is the adaptive immune response used? (2)

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Card 4

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The humoral component of adaptive immunity involves which soluble protein?

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Card 5

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