Clonal Selection and B cell Development Flashcards
How many types of antigen-specific receptors with unique specificity are on a lymphocyte?
Every lymphocyte has 1 type of antigen-specific receptor
What is required for lymphocyte activation?
Receptor binding
Recognition = action
This characteristic distinguishes lymphocytes from each other but not from their progenitor and progeny
Clonotypic
What is the importance of somatic recombination in clonal selection?
Creates more diversity in antigen-specific receptors than would be possible to encode in the human genome
What is the importance of non-polymorphic signalling molecules in B cells?
Transmit activation signals into B cell after antigen binds to antigen-binding site on B-cell surface
Triggers Ab production, differentiation, and proliferation
Is B cell development in the bone marrow antigen-dependent or independent?
Independent
At what stage will a B cell be selected against if it is self-reactive?
Immature stage
What is negative selection?
Step in immune system development that removes lymphocytes that are self-reactive
What will cause an immature B cell to undergo apoptosis?
Strong binding to self-antigen
What will happen to an immature B cell if it weakly binds to a self-antigen?
It will become anergic (functionally unresponsive)
Where does negative selection of B cells take place?
Bone marrow
What is required for B cells to switch isotypes?
Interaction with T-cells
What happens in parallel with isotype switching?
Somatic hypermutation
What is somatic hypermutation?
Process that happens to B cells after antigen exposure in lymphoid organs
Causes point mutations in variable regions of Ig made by exposed B cell —> tailored binding of Ig to that antigen
In what structure does isotype switching and somatic hypermutation take place in?
Germinal centers of the lymph nodes
What is the difference between somatic hypermutation and somatic recombination?
SH
Happens in the lymph nodes
Happens after foreign antigen exposure
Refine antigen-binding affinity of Igs
Exclusive to B cells
SR
Happens in bone marrow or thymus (B vs T cell)
Happens before antigen exposure
Makes unique BCR and TCR with diverse antigen specificity
Happens in both B and T cells
What is preserved in isotype switching?
Specificity
What changes with isotype switching?
Function
Distribution
This Ig is best for opsonization
IgG1
These 2 Ig are really good at complement activation
IgM
IgG3
This Ig is really good at moving across the epithelium
IgA
This Ig is really good at moving across the placenta
IgG1
