B cell lecture 2 Flashcards
B cell development and maturation
Pro B cell -> Pre-B cell -> Immature B cell
(Mature VDJ is complete)
B lymphocyte development in the periphery
Mature B cell
-> antigen stimulation
Activated B cell
->Differentiation
->IgM secreting plasma cells -> IgM Plasma cells secreting various isotypes
Memory B cells of various isotypes
IgG IgA IgE
B cell activation
By Helper T cell that respond to same antigen
2 types of B cell activation
Thymus Dependent
Thymus independent
Thymus dependent
T helper cell
Thymus independent
No T helper cell required
Thymus independent antigen mechanism
No T cell required
BCR complimentary antigen
Secondary antigen from same pathogen
Second signal
B cell activated
IgM
Thymus dependent antigen
BCR binds to antigen
Antigen internalised presented on MHC class II molecules
Helper T cell recognise MHC II through TCR
Release cytokines
B cell release antigen specific antibodies
Thymus dependent antigen B cell proliferation is facilitated by
CD4OL
IL4
What cytokine drives plasma cell
IL5
IL6
Where does B cell proliferation occur?
Germinal centres of the lymph nodes
Why do B cell become trapped temporarily?
T cell Zone
Contact with antigen + T helper cell
What is the germinal centres made up of?
Proliferating B cells
How many days after infection do B cell form?
7-10 days after an infection
What is the mantle zone?
Resting B cells displaced by activated B cells
What happens to B cells in germinal centre?
Somatic Hypermutation
Affinity maturation
Class Switching
Somatic Maturation
High antibody diversity
Point mutations V region -> light + heavy chain
Cystidine Deaminase
Intro nicks in the DNA that are repaired
Requires single strand of DNA
Targets DNA that is being transcribed Ig Genes
Affinity maturation
V region mutated, B cell selection based on ability to bind to antigen
Progression of somatic hypermutation antibodies become more specific
Summary affinity maturation
High affinity-> plasma cell -> antibody
-> memory cell
Low Affinity -> Cell Death
Clonal Selection
Antigenic Specificity
Antibody class switching
Early: IgM
DNA recombination
-> IgG IgA IgE
Different constant C region -> specific antigen binding region
How to generate specificity and diversity in bone marrow
Antigen independent
Pairing of different heavy and light chain
Recombination of V D J segments
Variability on the joins of the recombined gene segments
P and N region nucleotide addition
How to generate specificity and diversity in bone marrow in periphery
Antigen dependent
Somatic hypermutation
Class switching
Affinity maturation
Antibody functions
Neutralization
Opsonisation
Complement Activation
