B-cells Flashcards
1
Q
What are the key stages in B cell development
A
- haematopoesis in bone marrow: haematopoietic stem cells
- Pro-B cell stage: initiation of heavy chain rearrangement (D-J recombination, followed by V-DJ recombination)
- Pre-B cell stage: expression of the pre-B cell receptor, light chain rearrangement begins (V-J recombination)
- Immature B cell stage: expression of IgM B-cell receptor (BCR) on the cell surface, negative selection ensures auto reactive B cells are eliminated or undergo receptor editing
- Mature B cell stage: expression of both IgM and IgD on the surface, B cells exit the bone marrow and migrate to peripheral lymphoid tissues
2
Q
what are the key stages in B cell activation
A
- antigen recognition: naive B cells bind antigens via BCR
- Signal 1: BCR-antigen interaction triggers the activation of intracellular signalling
- Signal 2 (co-stimulation):
- thymus dependent activation: CD40:CD40L interactions
- Thymus-independent activation: TLR signalling or extensive BCR cross linking by repetitive antigen structures provides secondary signals - clonal expansion: activated B cells proliferate
- Differentiation: B cells differentiate into plasma cells (antibody-secreting) or memory B cells
3
Q
what are the roles of B cells in generating an immune response
A
- Antibody production
- Antigen presentation
- Cytokine secretion
- Formation of immunological memory
4
Q
What is the role of B cells in antibody production and what is the role of the Abs
A
plasma cells derived from activated B cells secrete antibodies:
- neutralise pathogens
- facilitate opsonisation, enhancing phagocytosis
- activate the complement system for pathogen destruction
5
Q
what is the role of antigen presentation by B cells
A
B cells process and present antigens via MHC-II molecules to CD4+ T helper cells
6
Q
What is the role of cytokine secretion by B cells
A
activated B cells secrete cytokines that modulate immune responses and enhance T cell activation
