IMI3: the adaptive immune system

Question 1

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

Answer 1

recognise pathogens specifically

memorise pathogens’ characteristics

Question 2

what are antigens?

Answer 2

part of a molecule recognised by an adaptive immune protein

Question 3

what are the 2 key features of adaptive immune system?

Answer 3

specificity and memory

Question 4

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

Answer 4

yes

Question 5

what are the humoral components of adaptive immunity?

Answer 5

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

Question 6

what produces antibodies?

Answer 6

B cells

Question 7

what are the best characterised lymphocytes?

Answer 7

conventional T cells and B cells

Question 8

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

Answer 8

thymus

BM

Question 9

what are naive B and T cells?

Answer 9

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

Question 10

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

Answer 10

they are going to become effector and/or memory cells

Question 11

what are the 2 functions of T cells?

Answer 11

support function: helper T cells

effector function: cytotoxic T cells

Question 12

what does B cell produce?

Answer 12

immunoglobulin/antibodies

Question 13

what are immunoglobulin?

Answer 13

molecules that bind highly specifically to foreign antigens

Question 14

do all B cells produce the same immunoglobulins?

Answer 14

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

Question 15

what do naive B cells express?

Answer 15

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

Question 16

what are plasma cells?

Answer 16

effector B cells that produce only antibodies but lack BCR

Question 17

can B cell act as an APCs?

Answer 17

yes

Question 18

do B cells express MHC?

Answer 18

yes MHC II

Question 19

how can they capture and internalise antigens?

Answer 19

through BCR

Question 20

what are TCR?

Answer 20

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

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

what are the key players of the humoral adaptive immunity?

Answer 23

antibodies

Question 24

what are the key players of cell mediated immunity?

Answer 24

T cells

Question 25

what are the 2 forms of immunoglobulin (Ig)?

Answer 25

BCR and antibodies

Question 26

what is the Ig domain?

Answer 26

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

Question 27

where is the antigen binding site?

Answer 27

on the end of the antibody

Question 28

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

Answer 28

IgG, IgA and IgD | IgE and IgM

Question 29

what is the role of the constant domain?

Answer 29

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

Question 30

what are the different functions of Ig?

Answer 30

activation of B cells | neutralisation of a viral pathogen before it can infect a cell

Question 31

what is the difference between BCR and antibodies?

Answer 31

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

Question 32

what is another name for antibodies?

Answer 32

soluble Ig

Question 33

what is another name for BCR?

Answer 33

membrane bound Ig

Question 34

what is the Fab domain?

Answer 34

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

Question 35

what is the Fc region?

Answer 35

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

Question 36

what are the different functions of antibodies?

Answer 36

opsonisation | complement fixation

Question 37

what is the complementarity-determining region (CDR)?

Answer 37

region of the Ig variable domain that contact the antigen

Question 38

what are the 5 classes of Ig?

Answer 38

IgG IgA IgM IgD and IgE

Question 39

what are the difference between the 5 classes?

Answer 39

size charge carbohydrate content the ay they assemble

Question 40

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

Answer 40

no

Question 41

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

Answer 41

IgM

Question 42

what does avidity means?

Answer 42

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

Question 43

what is affinity?

Answer 43

refers to the strength of binding at a single site

Question 44

how many binding sites does IgM have?

Answer 44

10 ==> high avidity

Question 45

what is the most abundant Ig in normal human serum?

Answer 45

IgG

Question 46

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

Answer 46

``` IgG1 IgG2 IgG3 IgG4 the heavy chain changes ```

Question 47

what are the 2 subclasses of IgA?

Answer 47

IgA1 and IgA2

Question 48

where can IgE be found?

Answer 48

bound to the surface of basophils and mast cells

Question 49

what does IgE do?

Answer 49

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

Question 50

where can we find IgD?

Answer 50

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

Question 51

what does IgD do?

Answer 51

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

Question 52

does TCR operate alone? if no with what?

Answer 52

no | operates with CD3 to form the TCR complex

Question 53

does TCR have a variable and constant region?

Answer 53

yes

Question 54

from where does the TCR recognise the antigen?

Answer 54

it recognises the whole antigen-MHC complex

Question 55

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

Answer 55

``` 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 ```

Question 56

can a cell present both MHC?

Answer 56

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

Question 57

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

Answer 57

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

Question 58

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

Answer 58

helper T cells | cytotoxic T cells

Question 59

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

Answer 59

diversification and adaptation

Question 60

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

Answer 60

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

Question 61

what are memory B cells?

Answer 61

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

Question 62

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

Answer 62

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