IMI3: the adaptive immune system Flashcards

1
Q

what are the 2 key consequences of the adaptive immune system?

A

recognise pathogens specifically

memorise pathogens’ characteristics

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2
Q

what are antigens?

A

part of a molecule recognised by an adaptive immune protein

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3
Q

what are the 2 key features of adaptive immune system?

A

specificity and memory

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4
Q

does the adaptive immune system have both humoral and cell mediated components?

A

yes

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5
Q

what are the humoral components of adaptive immunity?

A

antibodies that circulate in the blood perfuse tissues and are secreted onto mucosal surfaces

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6
Q

what produces antibodies?

A

B cells

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7
Q

what are the best characterised lymphocytes?

A

conventional T cells and B cells

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8
Q

what is the primary lymphoid organ for T cells? for B cells?

A

thymus

BM

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9
Q

what are naive B and T cells?

A

B and T cells that didn’t encounter an antigen upon encounter with an antigen

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10
Q

what happens to T and B cells after they are activated?

A

they are going to become effector and/or memory cells

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11
Q

what are the 2 functions of T cells?

A

support function: helper T cells

effector function: cytotoxic T cells

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12
Q

what does B cell produce?

A

immunoglobulin/antibodies

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13
Q

what are immunoglobulin?

A

molecules that bind highly specifically to foreign antigens

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14
Q

do all B cells produce the same immunoglobulins?

A

no. they each produce a unique immunoglobulin with a narrow specificity

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15
Q

what do naive B cells express?

A

membrane bound form of immunoglobulin called B cell receptor (BCR)

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16
Q

what are plasma cells?

A

effector B cells that produce only antibodies but lack BCR

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17
Q

can B cell act as an APCs?

A

yes

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18
Q

do B cells express MHC?

A

yes MHC II

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19
Q

how can they capture and internalise antigens?

A

through BCR

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20
Q

what are TCR?

A

T cell receptor that recognise antigens but ONLY when the antigen has been chopped up and held by an MHC molecule

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21
Q

what is another name for T helper cells? what do they do?

A

CD4–> important functions in supporting other cells of the adaptive immune system

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22
Q

what is another name for cytotoxic T cells? what do they do?

A

CD8–> specialise in killing defective host cells by releasing cytotoxic granules containing granzyme and perforin that can very effectively kill target cells

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23
Q

what are the key players of the humoral adaptive immunity?

A

antibodies

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24
Q

what are the key players of cell mediated immunity?

A

T cells

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25
Q

what are the 2 forms of immunoglobulin (Ig)?

A

BCR and antibodies

26
Q

what is the Ig domain?

A

smaller chunck of the immunoglobulin molecule which has a conserved structure held together with an internal disulphide bond

27
Q

where is the antigen binding site?

A

on the end of the antibody

28
Q

which types of Ig have 3 constant heavy domains? 4?

A

IgG, IgA and IgD

IgE and IgM

29
Q

what is the role of the constant domain?

A

determines the effector function of the Ig once an antigen is bound

30
Q

what are the different functions of Ig?

A

activation of B cells

neutralisation of a viral pathogen before it can infect a cell

31
Q

what is the difference between BCR and antibodies?

A

BCR has an extra transmembrane region in its C terminus that keeps the receptor anchored in the B cell’s plasma membrane

32
Q

what is another name for antibodies?

A

soluble Ig

33
Q

what is another name for BCR?

A

membrane bound Ig

34
Q

what is the Fab domain?

A

contains the variable region of the antibody ==> binds to antigens

35
Q

what is the Fc region?

A

contains the constant regions and is crucial for the effector functions of antibodies by binding to various antibody receptors called Fc receptors

36
Q

what are the different functions of antibodies?

A

opsonisation

complement fixation

37
Q

what is the complementarity-determining region (CDR)?

A

region of the Ig variable domain that contact the antigen

38
Q

what are the 5 classes of Ig?

A

IgG IgA IgM IgD and IgE

39
Q

what are the difference between the 5 classes?

A

size
charge
carbohydrate content
the ay they assemble

40
Q

does the V region change when the B cell changes the Ig class that it produces?

A

no

41
Q

what is the first Ig produced by B cell as they mature?

A

IgM

42
Q

what does avidity means?

A

overall strength of the binding of an antibody to an antigen with multiple binding sites

43
Q

what is affinity?

A

refers to the strength of binding at a single site

44
Q

how many binding sites does IgM have?

A

10 ==> high avidity

45
Q

what is the most abundant Ig in normal human serum?

A

IgG

46
Q

what are the 4 different subclasses of IgG? what’s the difference between those subclasses?

A
IgG1
IgG2
IgG3
IgG4
the heavy chain changes
47
Q

what are the 2 subclasses of IgA?

A

IgA1 and IgA2

48
Q

where can IgE be found?

A

bound to the surface of basophils and mast cells

49
Q

what does IgE do?

A

important in the response to parasitic helminth infections and plays a role in allergic diseases such as asthma and hay fever

50
Q

where can we find IgD?

A

in membrane bound form alongside IgM on the surface of naive B cells

51
Q

what does IgD do?

A

play a role In the activation of B cells prior to their differentiation into antibody-secreting cells

52
Q

does TCR operate alone? if no with what?

A

no

operates with CD3 to form the TCR complex

53
Q

does TCR have a variable and constant region?

A

yes

54
Q

from where does the TCR recognise the antigen?

A

it recognises the whole antigen-MHC complex

55
Q

what are the 2 types of MHC where can they be found and what do they do?

A
MHC class I --> present in all nucleated cells
it presents antigens from intracellular infection and peptides made during synthesis of cell proteins
MHC class II --> present in APCs
it presents antigens that come from proteins made outside the cell
56
Q

can a cell present both MHC?

A

yes if the cell is nucleated and is an APC (e.g. macrophages)

57
Q

how do T cells know if they are binding to MHC I or MHC II?

A

they have co-receptors CD8 (MHC I) and CD4 (MHC II)

58
Q

what are CD4+ T cells? CD8+ T cells?

A

helper T cells

cytotoxic T cells

59
Q

what are the 2 stages of the generation of TCRs and Igs variation?

A

diversification and adaptation

60
Q

what are the genes used to form the TCR of unconventional T cells?

A

gamma-delta T cells –> TCR-gamma and TCR-delta
BUT less diverse
MAIT cells and NKT cells –> alphabeta TCR

61
Q

what are memory B cells?

A

small proportion of B cells with high affinity ab return to a resting state similar to naive cells but can quickly proliferate differentiate to produce more plasma cells that rapidly produce antibodies to fight a second infection or the same kind

62
Q

what happens if a TCR binds to an antigen in the absence of additional danger signals like CD80 or CD86??

A

the T cell shuts down into a dormant state much harder to reactivate called a state of anergy