T Cell Dependent B Cell Responses

Question 1

What causes T cells to migrate towards the B cell zone in lymph nodes?

Answer 1

CXCR5

Question 2

What causes B cells to migrate towards the T cell zone in lymph nodes?

Answer 2

CCr7

Question 3

What is involved in the interaction between T cells and B cells?

Answer 3

T cells have CD40-Ligand and TCR. B cells have MHC complex and CD40`

Question 4

What is B cell isotype switching?

Answer 4

B cells start making antibodies with high affinity (IgM into IgG)

Question 5

What are long lived plasma cells?

Answer 5

make high affinity (IgG) antibodies

Question 6

What are long lived memory B cells?

Answer 6

don’t actively produce antibodies, but will when re-exposed to antigens and become plasma cells

Question 7

What are the steps of the germinal center reaction?

Answer 7

1) follicular T cell’s CD40-Ligand and TCR interact with the B cell’s CD40 and MHCII complex
2) B cells and T follicular cells both proliferate
3) Mutations induced by T follicular helper cells change the variable region of the B cell
4) Follicular dendritic cells present the antigen to the B cells. Only the B cells with IgG get signal to survive.
5) Surviving B cells will turn into long lived plasma cells and/or memory B cells`

Question 8

Explain how B cells goes from making IgM to IgG

Answer 8

B cells get signals from follicular helper T cells that allows mutations in the antigen binding regions (T helper cells change which form a new heavy chain (IgM into IgG). Then, only the high affinity variable regions ones survive from follicular dendritic cells

Question 9

Affinity maturation

Answer 9

changes in the variable regions that make a high affinity antibody

Question 10

Isotype switching

Answer 10

Heavy chains are being changed, but not the variable regions. IgM turns into IgG

Question 11

Switch regions on heavy chains

Answer 11

where T follicular cells cut to change the heavy chain of an antibody (isotype switching)

Question 12

Somatic hypermutation

Answer 12

When the VDJ region of B cell receptors changes during an immune response so only high affinity IgG survive.

Question 13

What allows the B cells and T cells to move into the follicle of lymph nodes after they interact with each other?

Answer 13

chemokine receptors (CXCR5)

Question 14

What all happens in the germinal center reactions?

Answer 14

1) Isotype switching by T helper cells (IgM into IgG) by cut/paste in heavy chain
2) affinity maturation by dendritic follicular cells (cause only high affinity IgG to continue to live)
3) long lived plasma cells made
4) memory B cells made

Question 15

Is the variable region affected during class switching?

Answer 15

No. Only the heavy chains (constant region) are changed to turn IgM into IgG

Question 16

Is antigen affinity a structural or functional difference between antibody types?

Answer 16

No. All the antibodies look the same (all are IgG)….just the less affinity ones will die off.