B Cells Flashcards
B cells produce antibodies. What do these antibodies act as when displayed on surface of B cell?
B cell receptors
What is needed to activate B cells?
Antibody-antigen interaction is not enough to activate
A second signal is needed
What is this second signal provided by?
T cells
Non-T cells (cytokines and interleukin provided by things like macrophages)
What happens once B cell is activated?
Will proliferate and release lots of same antibody into plasma
What is clonal expansion?
Proliferation of antigen-specific plasma cells
What is a plasma cell?
Mature version of B cell that secretes antibodies after it has been activated
What is clonal expansion followed by?
Somatic hypermutation, clonal selection and affinity maturation
What are memory cells?
Most highly-specific B cells produced by affinity maturation will be selected to become memory cells (remain in blood)
Number of memory cells increases after each reinfection
What antibody do plasma cells initially produce?
IgM
How do T cells activate B cells?
- Once T helper cells have been activated by their specific antigen, they differentiate into Th2 cells
- Th2 cells locate their corresponding B cell counterparts
- Provide B cell with second signal and release cytokines
How do Th2 cells locate their corresponding B cell counterparts?
Identifying the correct antigen within an MHC II on B cell’s surface
What is purpose of humoral immunity?
Specific adaptive immune response designed to fight extracellular infections
How do cytokines affect B cells?
Promote their development
What cytokines do Th2 cells release?
IL-2, IL-4 and IL-5
How do antibodies fight extracellular infections?
- Neutralise toxins by binding directly to them
- Bind to antigens on pathogens surface - agglutinates them and opsonises them
- Activates classical complement pathway
- Directly active effector cells (dendritic cells, NK cells, cytotoxic T cells)
