Immunology

Question 1

First stages of B-cell development (to immature B cell) (6)

Answer 1

Haematopoeisis
Haematopoetic stem cell -->
Common lymphoid progenitor -->
Early pro-B cell -->
Late pro-B cell -->
Pre-B cell -->
Immature B cell

Question 2

Central tolerance of B/T cells?

Answer 2

Deletion of cells as they bind to SELF antigens

Question 3

Virgin B cells express?

Answer 3

IgD and/or igM

Question 4

How long do lymphocytes stay in bloodstream?

Answer 4

1 hour

Question 5

% lymphocytes entering spleen after 1 hr?

Answer 5

45%

Question 6

% lymphocytes entering lymph nodes

Answer 6

40%

Question 7

How do lymphocytes leave the bloodstream into the lymph nodes?

Answer 7

Through high endothelial venules

Question 8

B cells stay where in lymph node? How long?

Answer 8

Primary follicles within cortex - 12 hours

Question 9

T cells where in the lymph node?

Answer 9

Paracortex

Question 10

Why do B cells go through HEV?

Answer 10

Due to cytokines - CCL21 and CCL19

Question 11

Why doe B cells go to cortex?

Answer 11

cytokines released by follicular dendritic cells - CXCL13

Question 12

B cells survival in cortex?

Answer 12

Contact with FDCs and stimulation by BAFF (cytokine)

Question 13

Ig H chain contains which gene segments?

Answer 13

V. D and J

Variable, diversity and joining

Question 14

Ig L chain contains which gene segments

Answer 14

V and J

Variable and joining

Question 15

Heavy chain gene rearrangement?

Answer 15

D to J recombination –> DJ
V to DJ recombination –> VDJ
Transcription

Question 16

When does H chain rearrangement take place?

Answer 16

From Pro-B cell to pre-B cell

Question 17

When does L chain rearrangement take place?

Answer 17

From pre-B cell to immature B cell

Question 18

Secondary diversification aka affinity maturation?

Answer 18

Somatic hypermutation
- point mutations in variable region can increase/decrease affinity
Class Switching
- either just of constant chain…IgM to IgD for example
- OR switching of subclasses of constant chain

High affinity binding is tested on FDCs
Low affinity–> apoptosis

Question 19

APCs?

Answer 19

Antigen presenting cells:
Dendritic cells
Macrophages

Question 20

APC function?

Answer 20

Phagocytose, process and present antigen on MHC

Question 21

T cell receptor recognise?

Answer 21

MHC (of APC) WITH foreign antigen bound

Question 22

B cell receptor recognise?

Answer 22

Soluble antigen and presented antigen

Question 23

T cell and MHC binding? (5)

Answer 23

• In lymph node…APC migrates there after binding peptide
• CD4+ cells bind to MHCII (helper)
• CD8+ cells bind to MHCI (cytotoxic)
• TcR has MHC and peptide binding sites
• Co-stimulating molecules produced by APC also activate (eg CD28)

Question 24

CD8+ binding?

Answer 24

Causes proliferation of cytotoxic T cells
Bind cells presenting foreign peptide
Release cytotoxic granules…death to foreign cell

Question 25

IL-2 causes?

Answer 25

Differentiation of T cells…clonal population of effector T cells

Question 26

IL-12?

Answer 26

Causes Th1 cells

Question 27

IL-4?

Answer 27

Th2 cells

Question 28

Th1 cells? (3)

Answer 28

Cellular immune system
Maximises “killing efficiency” of macrophages
Causes proliferation of CD8 T cells (cytotoxic)

Question 29

Th2 cells? (4)

Answer 29

Humoral immune response
B cell proliferation
Antibody class switching
Antibody production

Question 30

B cell and T cell interaction?

Answer 30

B cell presents antigen on MHCII
Encounter Th cells (Th2) and paracortex/cortex boundary
MHCII+antigen bind TcR
B cell proliferates

Question 31

B cells differentiation?

Answer 31

In apical light zone
Plasma cells:
- secrete antibodies (lots of RER), stay in lymph/spleen
- or in bone marrow - longer life

Memory cells:

• Express antibody on their surface
• In circulation