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Microorganisms + Disease > Adaptive Immunity in action L10 > Flashcards

Adaptive Immunity in action L10 Flashcards

1
Q

what do B cells make

A

antibodies

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2
Q

what do T cells make

A

CD4 helper T cells and CD8 cytotoxic T cells

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3
Q

what do T helper cells do

A

activate B cells

provide signals eg cytokines which can activate other immune cells, for example phagocytosis by macrophages

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4
Q

what do regulatory T cells do

A

suppress activity of other lymphocytes , to try and limit the damage caused by immune response

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5
Q

how are B and T cell receptors compared

A

Antibodies have light chain heavy chain

T cells alpha chain and beta chain

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6
Q

what do all nucleated cells have

A

MHC class I

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7
Q

what do only antigen presenting cells have

A

MHC class II

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8
Q

when can T cells recognise peptides

A

only recognise peptides when presented in a MHC molecule

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9
Q

what must primarily match in an organ transplant

A

primarily the MHC type that needs matching

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10
Q

what is somatic recombination

A

rearrangement of gene segments to give huge diversity in variable regions

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11
Q

what is the clonal selection theory

A

a single progenitor cell gives rise to large number of lymphocytes, each with different specificity
removal of potentially self-reactive immature lymphocytes by clonal deletion
pool of mature naive lymphocytes
proliferation and differentiation of activated specific lymphocytes to form a clone of effector cells

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12
Q

what are the postulates of clonal selection hypothesis

A
  • each lymphocyte bears a single type of receptor with a unique specificity
  • interaction between foreign molecule and lymphocyte receptor capable of binding that molecule with high affinity leads to lymphocyte activation
  • differentiated effector cells derived from an activated lymphocyte will have receptors of identical specificity to parental cell lymphocyte is derived from
  • lymphocytes with receptors specific for always present self molecules are deleted at each early stage in lymphoid cell development and are absent from repertoire of mature lymphocytes
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13
Q

what is the innate immune system response

A

inflammation
complement activation
phagocytosis
destruction of pathogen

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14
Q

how long after infection till innate immune response starts

A

minutes

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15
Q

how long does the innate immune response last

A

days

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16
Q

what is the adaptive immune response

A

interaction between antigen-presenting dendritic cells and antigen-specific T cells
antigen-specific B cells activated
memory T cells and effector form
T cell and B cell interaction
emigration of effector lymphocytes from peripheral lymphoid organs
elimination of pathogen by effector cells and antibody

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17
Q

what happens when there is is an interaction between antigen-presenting dendritic cells and antigen-specific T cells in adaptive immune response

A 
recognition of antigen
adhesion
co-stimulation
T-cell proliferation
differentiation
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18
Q

what happens when there is T cell and B cell interaction in adaptive immune response

A

formation of germinal centres
formation of effector B cells (plasma cells) and memory B cells
produce antibody

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19
Q

which parts of adaptive immune response take hours after infection

A

interaction between antigen-presenting dendritic cells and antigen-specific T cells
antigen-specific B cells activated

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20
Q

which parts of the adaptive immune response take days after infection

A

memory T cells and effector form

T cell and B cell interaction - antibodies produced

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21
Q

which parts of the adaptive immune response take a few days after infection

A

emigration of effector lymphocytes from peripheral lymphoid organs
elimination of pathogen by effector cells and antibody

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22
Q

which parts of the adaptive immune response last only days

A

interaction between antigen-presenting dendritic cells and antigen-specific T cells
antigen-specific B cells activated

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23
Q

which parts of the adaptive immune response last weeks

A

memory T cells and effector form
T cell and B cell interaction
emigration of effector lymphocytes from peripheral lymphoid organs
elimination of pathogen by effector cells and antibody

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24
Q

what is the immunological memory

A

maintenance of memory B cells and T cells and high serum or mucosal antibody levels
protection against reinforcement

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25
Q

how long does immunological memory response take after infection

A

days to weeks

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26
Q

how long does immunological memory last

A

can be life

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27
Q

what is the crucial role of dendritic cells

A

act as a crucial link between innate and adaptive immune systems
activating the adaptive immune response

28
Q

what can dentritic cells do

A

“talk” to lymphocytes

29
Q

where are immature dendritic cells

A

peripheral tissues

30
Q

where do dendritic cells migrate

A

via lymphatic vessels to regional lymph nodes

31
Q

where do mature dendritic cells activate molecules, and what

A

mature dendritic cells activate naive T cells in lymphoid organs e.g. lymph nodes

32
Q

what is the CD4 positive cell for

A

is a helper cell

33
Q

what is the antigen presented to

A

CD4 positive T

34
Q

how are CD4 positive proteins identified

A

protein called CD4 on their surface, a co-receptor which is required to enable interaction between their T cell receptor and MHC class II

35
Q

what dies the dendritic cell do to help activate T cells

A

produce soluble signals

36
Q

how does an activated T cell recognise B cell

A

activated helper T cell can recognise B cells that have a B cell receptor (surface-antibody) which has bound the same pathogen molecules and are presenting the same peptide

37
Q

how does the T cell activate the B cell

A

by both direct cell-to-cell interactions and soluble signals (cytokines)

38
Q

what does the activated B cell do

A

will then proliferate and price plasma cells which make large quantities of the specific antibody

39
Q

how do antibodies improve during infection

A

antibody affinity improves over an immune response

40
Q

what are plasma cells

A

terminally differentiated activated B cells

main antibody secreting cells of body

41
Q

what can dendritic cells, macrophages and B cells be called

A

antigen presenting cells

APC

42
Q

how are dendritic cells specialised

A

specialised in initiating adaptive immune response§

43
Q

how are dendritic cells activated, effect

A

PAMPS binding to PRR’s stimulate dendritic cells to engulf pathogen and degrade it intracellularly (phagocytosis) Can also take up virus particles and bacteria through receptor-independent macropinocytosis

44
Q

what mainly causes B cell activation

A

main cause: interaction with CD4 T helper cells

also, can be due to binding of free antigens

45
Q

what does B cell activation cause

A

optimal antibody response

46
Q

how are B cells activated by binding of free antigens

A

antigen-specific B cell binds antigen
specific antigen is efficiently internalised by receptor mediated endocytosis
high density of specific antigen fragments are presented at B-cell surface

47
Q

what are the effects of pathogen specific antibodies

A

Neutralize toxins
Block virus binding to cells
Opsonise pathogens
Activate complement

All aid in removal of pathogens

48
Q

what is Fc

A

Fragment crystallisable (Fc), it’s a portion of the antibody in the constant domain

49
Q

what happens in toxin neutralisation by antibodies

A

toxin binds to cell surface receptor
endocytosis of toxin:receptor complex
dissociation of toxin to release active chain which poisons cell
neutralising antibody blocks binding of toxin to cell-surface receptor

50
Q

what happens in pathogen oponisation (tagging) by antibodies

A

antibody binds to bacterium
antibody-coated bacterium binds to Fc receptors on cell surface
macrophage membrane surrounds bacterium
macrophage membranes fuse, creating a membrane-enclosed vesicle, phagosome
lysosomes fuse with phagosome, creating phagolysosome

51
Q

what is antibody dependent cell-mediated cytotoxicity used in

A

Can be used as a therapy – anti-CD20 monoclonal antibody eliminates some types of B cell tumors (rituximab)

52
Q

what happens in antibody dependent cell-mediated cytotoxicity

A

The monoclonal IgG antibody binds to cell surface protein CD20, and the Fc receptors on the NK cells can recognise this and lead to cell apoptosis

53
Q

how are viruses neutralised

A

virus binds to receptors on cell surface
receptor-mediated endocytosis of virus
acidification of endosome after endocytosis triggers virus and cell fuse and entry of viral DNA
antibody blocks binding to virus receptor and can block fusion event

54
Q

how are viruses replicated

A

To replicate viruses have to get genes into host cell

55
Q

how is bacteria neutralised

A

colonisation of cell surface by bacteria that bind to surface via bacterial adhesin
some bacteria become internalised and propagate in internal vesicles
antibodies against adhesins block colonisation

56
Q

what are the T cell effector functions (CD8+ cytotoxic T cell)

A

cytotoxic T cell recognises complex of viral peptide with MHC class I kills infected cell

57
Q

what are the T cell effector functions (CD4+ T helper cell)

A 
Th1 cell recognises complex of bacterial peptide with MHC class II, activates macrophage
T follicular helper cell recognises complex of antigenic peptide with MHC class II and activates B cell = antibodies
58
Q

how does CD8+ kill target cells

A

CD8 cells kill target cells by releasing the content of intracellular granules at the site of cell contact
CD8 T cells can kill cells bearing a specific antigen, whilst sparing neighbouring cells

59
Q

what granules does CD8+ T cells contain

A

perforin
granzymes
granulysin

60
Q

what does perforin do

A

aids in delivering contents of granules into cytoplasm of target cells

61
Q

what does granzymes do

A

serine proteases, which activate apoptosis once in cytoplasm of target cell

62
Q

what does granulysin do

A

has antimicrobial action, can induce apoptosis

63
Q

where are naive T cells

A

circulate though the blood and lymphoid organs

64
Q

when are T cells activated

A

after encountering antigen presenting cells showing a peptide/MHC complex

65
Q

what do activated T cells do

A

proliferate in the secondary lymphoid organs (lymph nodes, spleen etc) and two key sorts are produced: most become effector T cells which are actively involved in the immune response, a lesser proportion become long-lived memory T cells

Microorganisms + Disease (16 decks)

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