The Adaptive Immune System 1

Question 1

B cell receptor is bound to which coreceptor?

Answer 1

CD19, igalpha and beta

Question 2

Light chains are selective 2 types, which chromosomes?

Answer 2

Lambda
Kappa
Chromosome 2 and 22

Question 3

How many variable segments in heavy and light chain?

Answer 3

H-65

L-70

Question 4

How many diversity segments in heavy chain?

Answer 4

27

Question 5

What do light chains not possess?

Answer 5

Diversity segments

Question 6

How many possible combinations can be made in B cell?

Answer 6

100 trillion

Question 7

What do alpha chains in T cells not possess?

Answer 7

Diversity segments, similar to light chain in B cell

Question 8

How many possible combinations in T cell sequences?

Answer 8

Million trillion

Question 9

Why are there more T cell sequences at VDJ than B cells?

Answer 9

T cells don’t undergo further hypersomatic mutation hence more are required

T cell pool fixed from puberty

Question 10

Rearrangement of VDJ occurs at which sites?

Answer 10

Recombination signal sequences (RSS)
Contain: conserved segments of DNA composed of a hapatemer, spacer and a nonomer, 3’ of V segments and 5’ of J and both side of D segments

Question 11

Rearrangements is catalysed by which 2 enzymes?

Answer 11

Recombination activating genes RAG 1 and 2

Question 12

Steps in VDJ joining?

Answer 12

Cleavage
Repair/ diversity
Joining

Question 13

Skid mice lack which enzyme?

Answer 13

DNA dependent protein kinases

Question 14

Somatic hypermutation occurs where?

Answer 14

In a lymph organ

B cell encounters antigen, causing proliferation.

Question 15

How does somatic hypermutation occur?

Answer 15

In the hyper variable region of light and heavy chains, point mutations that are adjusting the receptor

Question 16

Are all affinities good?

Answer 16

After somatic hypermaturation, some have worse, better or same

Question 17

What is mutation rate?

Answer 17

1 base per 1000, which is 1 million times higher mutation rate than observed in normal cell division

Question 18

The billions of sequences that are not useful are where?

Answer 18

In introns

Question 19

Which enzyme drives somatic hypermutation?

Answer 19

Activation induced cytosine deaminase AID

Question 20

How does activation induced cytidine deaminase work?

Answer 20

Introduces uracil in the genetic code, which is spliced out and then replaced, usually a cytidine replacing

Question 21

What is affinity maturation?

Answer 21

Follicular dendritic cells present antigen to B cells than have undergone SHM.
Only those with high affinity

Question 22

In affinity maturation those B cells with low affinity will …?

Answer 22

Die, apoptosis

Question 23

What happens in class switch recombination?

Answer 23

Same receptor but different constant region

Question 24

IgA is adapted to penetrate?

Answer 24

Mucous membranes

Question 25

Why is class switch recombination needed?

Answer 25

Constant region can recruit different cell type to site

Question 26

How do you get igM and igD immunoglobulin?

Answer 26

In igD, the Mu segment is spliced off, In igM, delta segment spliced off

Question 27

In CSR, which is the first targeted switch region?

Answer 27

S mu

Question 28

For CSR which enzyme is needed?

Answer 28

AID

Question 29

Which CSR occurs in B cells is determined by?

Answer 29

Follicular T helper cells

Question 30

For neutralisation and diffusion in extra vascular sites which immunoglobulin is needed?

Answer 30

IgG

Question 31

What is igD good at?

Answer 31

Sensitisation of basophils

Question 32

What is igE good at?

Answer 32

Sensitisation of mast cells

Question 33

What is igA good at?

Answer 33

Neutralisation and Transport across epithelium

Question 34

What is igM good at?

Answer 34

Activation of complement system

Question 35

Average life of B cells?

Answer 35

5 days

Question 36

Negative selection?

Answer 36

When receptors bind to self antigen too strongly then are deleted

Question 37

Examples of thymus dependent and independent antigens?

Answer 37

Dependent- requires T cells to induce antibody production e.g proteins Independent e.g polysaccharides and lipids

Question 38

T cell independent responses only require which antibody?

Answer 38

IgM to detect simple repetitive antigens, modest affinity No memory B cells are activated by direct BCR crosslinking

Question 39

What is the signalling complex in the membrane for b and T cells?

Answer 39

Ig alpha and beta T cells- CD3

Question 40

B and T cell interaction

Answer 40

MHC to TCR CD80/CD86 to CD28 on T cells T cell activation leads to up regulation of CD 40 L which bind to CD 40 Cytokine production from T cells 3rd signal B cell proliferates and differentiates into antibody secreting B cell or becomes memory

Question 41

What does somatic hypermutation do?

Answer 41

Add point mutations

Question 42

The first switch region is always?

Answer 42

Su

Question 43

The second cut is determined by cytokines released by?

Answer 43

Follicular t helper cells