7. B Cells

Question 1

Which antibody isotype do naive B cells express first?

Answer 1

IgM

Question 2

How do isotype switching occur?

Answer 2

Class switching signals through cytokines that are produced by T helper cells

Question 3

IgG function?

Answer 3

All antibody functions:

1. Neutralisation
2. Agglutination
3. Opsonisation/Phagocytosis
4. Complement

Question 4

IgM function?

Answer 4

Complement activation

Question 5

IgA function?

Answer 5

Mucosal immunity mainly through neutralisation/agglutination

Question 6

IgE function?

Answer 6

• Eosinophil activation for helminth immunity

- Basophil/mast cell activation for allergy, histamine release

Question 7

ADA (adenosine deaminase) deficiency?

Answer 7

dATP builds up, which blocks transcription, which affects T and B cells as they’re mitotically active

Question 8

X-linked agammaglobulemia?

Answer 8

Mutation in protein Btk (Bruton’s tyrosine kinase), meaning mature B cells can’t be generated.

Treatment involved IVIG

Question 9

Selective IgA deficiency?

Answer 9

Failure of B cells to differentiate into IgA producing plasma cells.

• most common immunodeficiency
• recurrent infections bacterial/viral respiratory/Crohn’s disease/ulcerative colitis