4. adaptive immune system 1

Question 1

features of the innate response

Answer 1

rapid
pattern recognition receptors are germline encoded
increased cytokines, costimualtory molecules - instructive role for adaptive
direct response for host defences (phagocytosis, antimicrobial activity)

Question 2

features of the adaptive response

Answer 2

slow
recognition - initially low affinity receptors
influence from innate system - gene rearrangement, clonal expansion
response: T and B cells with receptors
has memory

Question 3

B and T cell development environments

Answer 3

specialised microenvirnoments
B cell - bone marrow, until terminal differentiation
t cell - thymus

Question 4

what happens to T cells after puberty?

Answer 4

thymus atrophies - only some residual thymocytes
new t cells generated extrathymic sites
long-lived peripheral t cell pool

Question 5

how and b and t cell developments guided?

Answer 5

stromal cells
t cells - compartmentalised, distinct types cortex and medulla
b cells - in bone marrow
both involve apoptosis

Question 6

lymphocyte differentiation

Answer 6

b cell 
-  lymphoid stem cell 
- pro-B lymphocyte 
- pre-B lymphocyte 
early B lymphocyte
activated B cell or plasma cell 

t cell 
- lymphoid stem cell
- early thymocyte 
- common thymocyte 
Th lymphocyte or Tc lymphocyte

Question 7

1st phase development

Answer 7

generation of antigen receptor

V(D)J gene rearrangement = antigen receptor

Question 8

2nd phase development

Answer 8

refinement of antigen receptor repertoire
antigen receptor tested for antigen recognition
positive and negative selection
occurs in primary lymphoid organs

Question 9

what happens during positive selection?

Answer 9

antigen receptor that recognises ‘self’ antigen weakly

Question 10

what happens during negative selection?

Answer 10

antigen receptor that binds strongly to ‘self’ antigens is eliminated via apoptosis

Question 11

3rd phase development

Answer 11

stimulation by foreign antigen
clonal selection of lymphocytes
generation of effector and memory lymphocytes
occurs in secondary lymphoid organs

Question 12

thymus dependent antigens

Answer 12

b cells are dependent on helper t cells to induce antibody production
eg proteins

Question 13

thymus independent antigens

Answer 13

cells do not need t helper cells to induce antibody production
eg polysaccharides, lipids

Question 14

t cell independent responses

Answer 14

simple repetitive antigens (often carbs)
mostly IgM (+IgD on naïve B cells)
modest affinity
b cells activated by direct b cell receptor cross linking
also can be activated by toll like receptors

Question 15

t cell/b cell collaboration

Answer 15

required for antibody response to complex antigens
requires direct b-t cell interaction
involves multiple surface receptors on t and b cells
both cells must recognise antigen
both need signal 1 and signal 2

Question 16

t cell dependent b cell response

Answer 16

antigen binds to b cell receptor = signal 1 to b cell
antigen is internalised, processed and antigenic peptides displayed on MHC
t helper cell recognises antigen-MHC complex via t cell receptor = signal 1 to t cell
cd80/cd86 on b cell binds to cd28 on t cell = signal 2 to t cell
t cell activation leads to up regulation of cd40 ligand
cd40l binds to cd40 on b cell = signal 2 to b cell
cytokine production by t cell helps activate b cell
b cell proliferates and differentiates into antibody secreting b cell (plasma cell)

Question 17

b cell antigen recognition

Answer 17

form antigen receptor by V(D)J recombination - 2 heavy chains, 2 light chains (membrane and secreted) signal by associating with signalling complex in membrane = Ig-alpha and Ig-beta
can bind to intact protein antigen in solution

Question 18

t cell antigen recognition

Answer 18

form antigen receptor by V(D)J recombination - alpha-beta heterodimer (membrane only)
signal by associating with signalling complex in the membrane = CD3 complex
binds peptides displayed on surface of antigen presenting cell