Lecture 28

Question 1

What happens in the lymph node (B cell)

Answer 1

B cell activation, differentiation, and proliferation, but in different parts

Question 2

Overall what happens in subcapsular sinus

Answer 2

Where T cells encounter antigen
Where Subcapsular macrophages (SCS macrophages) are located
Most superficial

Question 3

Overall what happens in T cell zone

Answer 3

Where T cell gets activated by interacting with dendritic cells
In-between B cell zone and medulla

Question 4

Overall what happens in B cell zone

Answer 4

Where B cell encounters Antigen and undergoes later stages of proliferation, differentiation
Includes B cell follicles and germinal centers
In-between Subcapsular sinus and T cell zone

Question 5

Overall what happens at T-B border

Answer 5

Where B cells first receives signal 2
Border between T and B cell zones

Question 6

What happens in the follicle

Answer 6

Place of development and activation of B cells
A part of B cell zone
Surrounds germinal center

Question 7

What happens in Germinal Center

Answer 7

Intense B cell proliferation and differentiation
Within Follicles on the B zone

Question 8

Process of B cell activation

Answer 8

1) In B cell zone: B cell encounters Antigen on SCS macrophage, free-floating antigen, OR on follicular dendritic cells
2) BCR:Ag is internalized and processed
3) Increased expression of MHC II
4) Increased expression of chemokine receptor (brings B cell to T-B border)
5) At T-B border: B cell receives signal 2–>gets activated

Question 9

2 Paths of activated B cells

Answer 9

1) Form primary focus in subcapsular region–>plasmablast or IgM memory B cell
2) Migrate to follicle to form Germinal Center–>plasma cell

Question 10

Description of Naive B cell

Answer 10

Have IgM on surface
Do not secrete antibody

Question 11

Description of Plasmablasts

Answer 11

Secrete large numbers of antibodies
Can no longer proliferate
Little to no surface BCR expression

Question 12

Description of Plasma Cell

Answer 12

Can secrete antibodies
Can proliferate
Still has BCRs

Question 13

Main outcomes from Primary Focus pathway

Answer 13

1) Plasmablast–> early antibody production
2) IgM+ Memory B Cell–>production of IgM

Question 14

Where are primary focuses formed

Answer 14

Near subcapsular zone or in Interfollicular Regions or Medullary cords

Question 15

What incudes the formation of a primary focus

Answer 15

Once activated B cell receives signal 1 and signal 2

Question 16

What happens within a primary focus

Answer 16

Activated B cell proliferate and differentiate into plasmablasts

Question 17

When are primary foci apparent

Answer 17

5 days after a primary infection

Question 18

Plasmablast characteristics

Answer 18

1) B cells that secrete antibody
2) Responsible for early antibody production
3) Produce IgM (lower affinity)
4) Majority due by apoptosis within 5-10 days
5) Some can migrate to bone marrow and become plasma cells (where they will continue antibody production)

Question 19

Main outcomes of Germinal Center pathway

Answer 19

1) Plasma cells–>secretes large quantities of antibodies
2) Memory B cell–>memory to maintain capacity to produce higher affinity antibodies

Question 20

What happens within Germinal Centers

Answer 20

B cells receive signals 1 and 2 AGAIN
B cells undergo differentiation and processes to produce more effective and higher affinity antibodies

Question 21

What type of B cell differentiation takes place within Germinal Centers

Answer 21

1) Somatic hypermutation
2) Affinity maturation
3) Class switching

Question 22

When does Germinal Center size peak?

Answer 22

7-12 days after antigen stimulation

Question 23

Where do Plasmablasts reside

Answer 23

Stay in lymph node to secrete antibodies

Question 24

Where do Plasma cells reside

Answer 24

Stay in medulla of lymph node OR
Travel to bone marrow and stay to produce antibodies
Have higher affinity than plasmablasts