L18 - B Cells - Cellular Interactions and Trafficking

Question 1

What are the different subsets of B cells?

Answer 1

B1 and B2 cells

• B1 - No memory, part of the humoral immune response. First produced in the fetus and undergo self-renewal in the periphery
• B2 - Traditional bone marrow produced B cells

Question 2

What are the two different types of B2 B cells?

Answer 2

• Follicular B-2 Cell

- Marginal B-2 Cell

Question 3

What are the characteristics of marginal zone B cells?

Answer 3

Largely non recirculating, enriched in marginal zone of the spleen
- Very early participation in immune response, limited diversity, lower threshold for activation

Question 4

What are the characteristics of follicular B cells?

Answer 4

Form majority of mature B cells (~95%)

• Co express IgM and IgD
• Recirculation
• Higher threshold for activation

Question 5

What are the three roles of antibodies?

Answer 5

• Neutralization
• Opsonization
• Complement Activation

Question 6

How does antigen reach naive B cells?

Answer 6

• Opsonized antigen entering lymph nodes bind to complement receptors on surface of macrophages present in subcapsular sinus
• Allows B cells to encounter / also allow transport to follicle to become localized on surface of follicular dendritic cells

Question 7

How do B cells and T cells find each other?

Answer 7

• Recognition of cognate antigen by B cells leads to CCR7 upregulation (T-cell zone)
• T cells activated by antigen express CXCR5 migrating it towards the follicle
• B cells also express CXCR5 (responds to CXCL13) bringing it to the border hence they meet

Question 8

Where are germinal centres found?

Answer 8

Lymph nodes and spleen

Question 9

What occurs in germinal centres?

Answer 9

Somatic hypermutation and class switching

Question 10

What zones are there and what occurs where?

Answer 10

Dark zone - somatic hypermutation and proliferation

Light zone - Class switching