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Neural Biology 1 > immune responses > Flashcards

immune responses Flashcards

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1
Q

what are B- cells responsible for ?

A

. responsible for production of antibodies

. referred to as antibody mediated immunity

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2
Q

what are T-cells responsible for ?

A

T-cells are responsible for what is referred to as cell-mediated immunity and that includes the destruction of infectious cells and the the activation of various immune cells

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3
Q

what are major histocompatibility complex?

A

.molecules that the immune system uses for recognition
. system that allows immune cells to recognise infected cells
. system used for differentiating between self and non-self

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4
Q

what does the B-cell response consist of ?

A

. antigen recognition
. activation
. cell division
. differentiation into AFC=antibody forming cells ( plasma cells )

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5
Q

explain the B-cell response ?

A

. antigen recognition - B cells have antigen receptors on their surface, antigen receptor on B cell is an antibody , once antigen is recognised by B cell , the B-cell becomes activated which is described as clonal selection - which is specific for the particular target , the pathogen that the immune system needs to deal with , then that is selectively activated and then there is a process of amplification of the immune system where we have an increase in cell division , then the B-cells differentiate into antibody forming cells and we refer to those antibody forming cells as plasma cells

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6
Q

what is the B-cell response regulated by ?

i.e. what is antigen recognition , activation , cell division and differentiation into AFC regulated by ?

A

. regulated by a series of proteins
which are referred to as cytokines and these are chemicals signals that trigger those various aspects of the B-cell response

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7
Q

what type of signals do some antigens need for a B-cell response to occur ?

A

for certain antigens in order for B-cell response to occur they require signals from a particular population of T-cells called t-helper cells

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8
Q

what is clonal selection ?

A

. selection of the appropriate lymphocyte whether there is a good fit between the lymphocyte receptor ( anti-body receptor on surface of B-cell ) and the antigen , then that lymphocyte is then selected and selectively amplified in terms of the process of cell division and then those cells then differentiate into the antibody forming cells ( plasma cells )
. we also lay down a selection of memory cells such that the immune system can respond more rapidly and much more enhanced way following the second exposure to that particular antigen

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9
Q

what are memory cells ?

A

memory cells when exposed to an invading pathogen replicates itself and remains in the lymph node searching for the same antigen

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10
Q

explain the primary and secondary antibody response ?

A

. starts from time 0 , that’s the point where the primary antigen challenge occurs
. y-axis is measuring anti body concentration
. nothing happens in the first few days - the lymphocytes are undergoing a process of cell division to get this critical mass to produce enough antibody to be detected
. then we get that initial rising phase of antibody response - that is a particular subtype of antibody known as IgM
. as IgM response begins to fade is being taken over by the IgG response
. once antibody dealt with the infection , the antibody levels start to fall down to 0
. following the second antigen challenge( second dose ) the latency is shorter , you can see that the IgG response which rises more rapidly , with much higher levels of antibody following that secondary antigen challenge and this is the bases of vaccination

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11
Q

what is the basic structure of an antibody ?

A
  • consists of 4 polypeptide chain
  • 2 identical heavy( longer ) chains and 2 identical light ( shorter ) chains
  • linked by disulfide bonds
  • variable ( amino acid composition is variable ) and constant domains ( amino acid composition is constant )
  • the variable region ( Fab) confers antigen recognition - antigen binding sites
  • constant region ( Fc) interacts with cell surface receptors and activates complement system
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12
Q

what are the 5 classes of antibody ?

A
  • 5 classes and each has characteristic property
  • they also vary in structural complexity
  • Ig= immunoglobulin
    1- IgG - relatively simple y-shaped molecule consisting of two light chains and two heavy chains

2- IgA

3- IgM - complex molecule which consists of a five antibody subunit

4- IgD

5- IgE

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13
Q

what are the 3 distinct antibody functions?

A

antibody function in 3 distinct ways
. bind directly to pathogens preventing then from entering or damaging healthy body cells

. neutralize bacterial toxins

. binding antibody to antigen is the trigger to activate complement system

. facilitate phagocytosis by opsonization - the coating of phagocyte target with antibody which enhances phagocytosis - and that happens because phagocytes have antibody receptors on their surface so it allows the phagocyte to specifically bind to its target

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14
Q

what is the function of IgG which is a major immunoglobulin ?

A

. major serum Immunoglobulin
. the only antibody that is able to cross the placenta and thats important for conferring immunity to the developing foetus
. also responsible for immune protection in the early weeks of life

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15
Q

what is the function of IgM ?

A 
. it's a more complex molecule - pentamer of basic 4 polypeptide structure 
. 1st class produced in the immune response 
. activates complement effectively
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16
Q

what is the function of IgD?

A

. cell surface receptor on B cells - which acts as antigen receptor

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17
Q

what is the function of IgA ?

A

. dimer of basic structure - 2 antibody molecules linked together
. most abundant Ig in external secretions ( tears and saliva )

18
Q

what is the function of IgE ?

A

. Fc receptor binds to mast cells and basophils

. important in allergy

19
Q

explain the antibody response ?

A

. the initial antibody response following a primary antigenic challenge involves IgM
. as IgM levels fall the levels of IgG begin to rise
. secondary antigenic challenge involves a rapid IgG response - antibody response is much more rapid in secondary response due to memory B-cells

20
Q

what is the function of dendritic cells in secondary lymphoid ?

A

. dendritic cells in secondary lymphoid tissues act as long-term repositories of antigen

. memory B-cells are maintained by recurrent signals from these cells

21
Q

explain what happens in vaccination ?

A
  • the vaccine is presenting an inactivated version of the pathogen to the immune system to trigger a primary response , they are deactivated so they don’t cause a disease , but they are laying down this population of memory cells which allows the immune system to work more efficiently and rapidly following contact with the pathogen
22
Q

what does the T-cell response consist of?

A

the T-cell response consists of

  • antigen recognition
  • activation signals
  • cells division
23
Q

what are the two distinct population if T- lymphocytes ?

A
  • T- helper cells which are responsible for secreting cytokines that are involved in immune regulation
  • cytotoxic T cells which are responsible for destroying infected or target cells
24
Q

what is the receptor for T lymphocytes ?

A

. T cells receptor is more complex and T cell receptor will only recognise antigens when their presented to it via MHC protein

25
Q

what are MHC ?

A

( major histocompatibility complex molecule )- these are cell surface glycoproteins that are involved in the process of
antigen recognition and play important roles in interactions amongst immune cells

26
Q

explain presentation to cytokines T cells ?

A

. MHC molecule present peptide
. the antigen peptide bound on MHC molecule
. T-cell receptor which cytokines T - cells recognises MHC and peptide and trigger cell destruction

27
Q

explain presentation to T helper cells ?

A

. antigen is taken up by an antigen presenting cell
. antigen is processed by that cell and then presented to T helper cells through the cell surface protein ( MHC ) , that is then recognised by the T - cell receptor which then causes activation of T cells

28
Q

what are the two varieties of the MHC molecules ?

A
  • class 1 gene products found on all nucleated cells and participate in antigen presentation to cytotoxic T cells - this the process that our body uses initially for differentiating between self and non-self , our immune system has learnt to recognise the MHC 1 proteins on the surface of our body cells
  • when there is an alteration in the composition of a cell ( i.e. tumour cells ) its then viewed as a target for immune system
  • class 2 gene products found on antigen presenting cells and participate in antigen presentation to T helper cells
29
Q

what are the MHC molecules coded by ?

A

. coded by a series of genes on chromosome 6

30
Q

how many types of molecules are in the class 1 region of the MHC ?

A 
. 3 types of class 1 molecules 
. the class 1 region consists of HLA ( human leukocyte antigen ) - A , B and C loci 
. known as human leukocyte antigen because the early work in these proteins was done in leukocyte white blood cells
31
Q

how many type of molecules are in the class2 region of the MHC ?

A 
. 3 types 
the class 2 region is divided into HLA-DP , DQ and DR sub regions
32
Q

what is the function HLA molecules ?

A 
. HLA antigens are important for the ability of T cells to differentiate between self and non-self ( Tc cells are able to differentiate between self and non-self MHC class 1 molecules and foreign non-self molecules 
. HLA antigens are highly polymorphic with multiple genetic variants which differ from one person to another 
. in organ transplant  there needs be close matching between the MHC class one molecules of host and donor to reduce risk of rejection - but px still need to be on powerful immunosuppressant drugs to decrease reduction
33
Q

what are the memory T-cells ?

A

. following a T-cell response memory T-cells are laid down
. T-cell memory exit for both T helper and cytotoxic T-cells
. these are maintained by repeated stimulation by APC
. the population of memory T cells is maintained over time

34
Q

what is cell co-operation ?

A

. both anti-body mediated immunity and cell - mediated immunity happen together in a coordinated way
. T -helper cells is being activated through the process of antigen presentation so the antigen is taken up bay an antigen presenting cell , its presented to the T cell receptor through MHC protein and once activated the t-helper cell releases cytokines that are involved in the process of call activation and immune regulation

35
Q

how to describe the complement system ?

A

. we describe the complement system with respect to the innate system
. it’s an enzyme system - in which the product of one reaction forms the enzyme for the next
. is made up of a series of protein component ( 35 protein component ) and these are all given a C prefix which stands for complement and a number which designates the particular complement complement

36
Q

how is the complement system activated ?

A

. complement can be activated through the innate system so certain molecules on the surface of microorganisms are able to activate the complement pathway through an alternative pathway

. can also be activated by the coming together of antigen and antibody forming an antigen - anti body complex

37
Q

what is the central enzymatic reaction in the complement system ?

A
  • the conversion of C3 molecule into C3a and C3b
  • this is the creation of a proteolytic enzyme that’s either generated through the alternative or the classical pathway that cleaves the C3 molecule into two components
  • C3b goes on to trigger the terminal complement sequence
38
Q

what are the various roles of the complement system components ?

A

. classical and alternative pathways generate a C3 convertase which cleaves C3 into C3a and C3b

. C3b acts as an opsonin - enhancement of phagocytosis

. C3b can cleave C5 into C5a and C5b

. C5b can deposit on membrane and activate the lytic pathway via the membrane attack complex ( MAC )

. C3a and C5a act as mediators of inflammation

39
Q

what are the 3 distinct roles of the complement system ?

A

. enhance phagocytosis ( opsonization )
. stimulates inflammatory reactions
. membrane damage to pathogens

40
Q

what is AMD ( age related macular degeneration ) relation to complement system ?

A
  • is progressive retinal disease and major cause of irreversible vision loss in the elderly
  • complement system plays a major role in the pathogenesis of AMD
  • genetic studies of AMD have suggested that variants in C3 and certain complement regulatory proteins (complement factors CFH and CFI ) might influence susceptibility to this disease

Neural Biology 1 (58 decks)

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