B cell immunity

Question 1

B cell receptors

Answer 1

B cell receptors - antigen is bound to the B-cell by the antibodies, the antibody binds to antigenic determinant (epitope) on surface

Question 2

Antigen is internalised and degraded

Answer 2

1) antigen is bound to Ab on cell surface
2) B cell is activated & internalises antigen
3) antigen is degraded to short polypeptides
4) Binds to MHC class II molecules

Question 3

B cell presents antigen to T helper cells

Answer 3

1) Antigen is presented to activated CD4+ in association w MCH class II
2) T cells must be responding to antigens w the same molecular complex
3) Process known as linked recognition

Question 4

Helper T cells activate B cells to produce antibodies

Answer 4

T cell that recognises same antigen stimulated and produces cytokines
Cytokines stimulates B cell proliferation and IgM production
Somatic hypermutation also takes place, leading to increased antibody affinity and class switching

Question 5

Where does B cell activation typically take place?

Answer 5

Secondary lymphoid tissue

Question 6

Plasma cells

Answer 6

Responsible for antibody production
Leave the germinal centre and migrate to inflamed tissue

Question 7

Somatic hypermutation

Answer 7

introduces point mutations throughout the V region

Question 8

Somatic recombination

Answer 8

produces diversity through gene rearrangement, junctional diversity, and addition of nucleotides

Question 9

Key enzyme of hypermutation

Answer 9

Activation Induced cytidine Deaminase (AID)

Question 10

T independent B cell responses

Answer 10

Mostly IgM
2 types:
Ti-1 - B cell mitogens bacterial lipopolysaccharide (LPS), which activates through TLR4
Ti-2 - repeated antigen structure - bind antibody and cross link, activating B cell