B Lymphocytes Flashcards
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
