T1 L4 Adaptive immunity 1

Question 1

Describe the innate response

Answer 1

Rapid response
Pattern-recognition receptors
Increased cytokines and costimulatory molecules
Direct response for host defence - phagocytosis, antimicrobial activity

Question 2

Describe the adaptive response

Answer 2

Slow response
Recognition - initially low affinity receptors
Gene rearrangement and clonal expansion
Memory

Question 3

How many B cells circulate in the body?

Answer 3

10 billion

Question 4

How many B cells are made everyday?

Answer 4

10 million

Question 5

What is the lifespan of an immature B cell?

Answer 5

5 days

Question 6

Where do B cells develop?

Answer 6

Bone marrow

Question 7

Where do T cells develop?

Answer 7

Thymus

Question 8

Describe T cell production in adults

Answer 8

Thymus has atrophied
Thymus has some residual corticomedullary tissue with myocytes
New T-cells are generated in extrathymic sites
Long-lived peripheral T-cell pool

Question 9

Describe the involvement of stromal cells in the development of T cells

Answer 9

Development is compartmentalised

Distinct types of stroll cells

Question 10

Describe the involvement of stromal cells in the development of B cells

Answer 10

Stromal cells are in the bone marrow

Question 11

Describe the pathway of T lymphocyte development from the lymphoid stem cell

Answer 11

1) Lymphoid stem cell
2) Pro-T lymphocyte
3) Early thymocyte
4) Common thymocyte
5) Th lymphocyte, Tc/s lymphocyte

Question 12

Describe the pathway of B lymphocyte development from the lymphoid stem cell

Answer 12

1) Lymphoid stem cell
2) Pro-B lymphocyte
3) Pre-B lymphocyte
4) Early B lymphocyte
5) Activated B lymphocyte, plasma cell

Question 13

What are the 3 stages of B cell development?

Answer 13

Phase 1: generation of antigen receptor
Phase 2: refinement of antigen receptor repertoire
Phase 3: stimulation by foreign antigens

Question 14

Describe the 1st phase of B-cell development

Answer 14

Generation of antigen receptor

- V(D)J gene rearrangement –> antigen receptor

Question 15

Describe the 2nd phase of B-cell development

Answer 15

Refinement of antigen receptor repertoire

• antigen receptor is tested for antigen recognition
• positive selection for antigen receptor that recognises ‘‘self’’ antigens weakly
• negative selection for antigen receptor that binds strongly to ‘‘self’’ antigens. Cells eliminated via apoptosis

Question 16

Describe the 3rd phase of B-cell development

Answer 16

Stimulation by foreign antigens

• clonal selection of lymphocytes
• generation of effector and memory lymphocytes

Question 17

Describe thymus dependent antigens

Answer 17

Dependent upon helper T-cells to induce antibody production

Recognises proteins

Question 18

Describe thymus independent antigens

Answer 18

Doesn’t need helper T cells to induce antibody production

Recognises polysaccharides and lipids

Question 19

Describe the 2 signal model for B-cell antigens

Answer 19

Engagement of antigen receptor (signal 1) isn’t sufficient to activate B-cell
Need co-stimulatory signal (signal 2), CD40/CD40L

Question 20

Describe the 2 signal model for T independent antigens

Answer 20

Polymeric complexes of B cell receptors on surface of cell bind together to cross link antigens they are binding. Amplifies signal B cell receives. Autoactivation of B cell

Question 21

Describe the 2 signal model for T dependent antigens

Answer 21

More common
Only a few receptors on surface can recognise the antigen, they don’t polymerise but lead to internalisation of that antigen

Question 22

Describe the T-cell independent response

Answer 22

Simple, repetitive antigens - often carbohydrates
Mostly IgM
Modest affinity
No memory
B cells activated by direct B-cell receptor cross linking and aggregation
B cells can also be activated via Toll-like receptors

Question 23

Describe the B cell development (antigen dependent)

Answer 23

T-cell / B-cell collaboration
- required for antibody response to complex antigens
- requires direct, physical B-T interaction
- involves multiple cell surface receptors on T and B cells
- Both B & T cells must recognise antigen
- Both B & T cells need signal 1 and signal 2
Class switch recombination

Question 24

Describe the steps of the T-cell dependent B-cell response

Answer 24

1) Antigen binding to B cell receptor provides ‘‘signal 1’’ to B cell
2) Antigen is internalised & processed. Antigenic peptides displayed on MHC for T-cell recognition
3) Th (helper T-cell) recognises antigen MHC complexes via T-cell antigen receptor & provides ‘‘signal 1’’ to T-cell
4) CD80 / CD86 on B-cell bind to CD28 on T cell to provide ‘‘signal 2’’ on T cell
5) T-cell activation leads to up regulation of CD40L which binds to CD40 providing ‘‘signal 2’’ on T-cell
6) Cytokine production by activated T cells also help activate B cell
7) B cell proliferates and differentiates into antibody-secreting B cell (plasma cell)

Question 25

What is the signalling complex for B cells?

Answer 25

Ig-alpha

Ig-beta

Question 26

What is the signalling complex for T cells?

Answer 26

CD3 complex

Question 27

What is the initial lag of the primary antibody response?

Answer 27

5-10 days

Question 28

What is the initial lag of the secondary antibody response?

Answer 28

1-3 days

Question 29

What is the peak response of the antibody responses?

Answer 29

Primary response: smaller

Secondary response: larger

Question 30

What is the antibody isotype in the primary antibody response?

Answer 30

Usually IgM > IgG

Question 31

What is the antibody isotype in the secondary immune response?

Answer 31

Relative increases in IgG & under certain situations in IgA or IgE