B Lymphocytes Flashcards Preview

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Flashcards in B Lymphocytes Deck (13):

What types of epitopes do T and B recognise?

T = the sequence
B = the tertiary structure


Describe the structure of the BCR

Membrane anchored antibody and disulphite linked hetrodimers Igalpha and Igbeta
The Igalpha and beta have tails long enough to signal in the B cell


Describe immunoglobulin gene rearrangement

Separate multigene families on different chromosomes
Segments are rearranged to produce different BCRs and TCRs


Describe light chain expression of BCR

Only V and J
70 variable units
Immature B cell has germline DNA
Loses some units leaving a few V and J regions = random
Splicing then adds to variation in BCR


What enzyme is used for DNA recombination?

V(D)J recombinase
Coded for rag genes
Deficiency in rag genes = SCID


Heavy chain expression

V, J and D
Germline DNA is shuffled and rearranged
Constant region determines type of antibody G,A,M,D,E
Heavy chain is rearranged first them light


3 things that can happen once B bound to antigen

Affinity maturation = antibody response improves
Memory cell
Plasma cell


What does a naive cell need to activated?

Antigen and accessory signal
Either T cell dependent or independent


T cell dependent activation

BCR binds to antigen
Internalises it and breaks it down
Presents MCH class II with antigen on it
Detected by CD4 on helper T
T undergo clonal selection and go to lymph nodes
B cell activated


T cell independent

BCR recognises antigen
IgM recognises PAMPs
B cell activated


How do cytokines influence Ig class?

2 types of T cells
They produce different cytokines
This switches the exons in the constant regions to switch Ig classes


Why does the immune response improve between primary and secondary?

Somatic hypermutation and affinity maturation
Activation induced deamination causes point mutations in the VDJ region = changes to B cell


What if B cells go bad?

Antibodies are involved in autoimmune disease
Some become lymphomas