chapter 9 Flashcards
The α and γ chain are similar in structure to the antibody ____________
light chain
The β and δ chain are similar in structure to the antibody ________________
heavy chain
What mechanisms also control whether the cell produces membrane-bound or secreted IgM?
mRNA splicing
Why does blood cell development change locations?
bone marrow isn’t formed right at fertilization
Hematopoiesis stages are defined by:
cell-surface markers, transcription factor expression, and Ig gene rearrangements
_________________in the bone marrow provide support and growth factors to developing cells
stromal cells
Describe the pre-B-cell receptor:
-expressed in early pre-B stage
-heavy-chain rearrangement is finalized
-Ig heavy chain complexed with VpreB and λ5 (SLC)
Late pre-B stage is marked by:
initiation of light-chain gene rearrangement, then completion
IgM receptor is expressed on the cell surface, transitioning the
cell into_______________
immature B-cell stage
Immature B cells in the bone marrow are exquisitely sensitive to _______________ induction.
tolerance
Immature B cells bear membrane ___________________
IgM, B220, CD25, IL-7R, and CD19
What are the three possible outcomes after surface receptors are tested against self-antigens?
-clonal deletion of strongly autoreactive cells
-receptor editing
-anergy
how does clonal deletion of strongly autoreactive cells occur?
-through apoptosis
-termed central tolerance as it occurs in bone marrow
what is receptor editing?
reactivation of recombination machinery
what is anergy?
induction of nonresponsiveness to further stimuli
(even self-antigen stimuli)
What happens to the self-reactive B cells that don’t undergo deletion?
Some are released to the periphery and subject to
further round of selection
What are the two subsets of immature B cells?
Transitional B cells— T1 and T2
Transitional B cells differ in gene expression as they progress through the ________________ for further maturation.
spleen
The T1 subset is still undergoing screening, possessing the possibility of a ____________________ event.
negative selection
Mature, primary _________B cells migrate to the lymphoid follicles.
B-2
What antibodies are expressed on the surface of B-2 B cells?
IgM and IgD
Describe B-2 B cells:
– Recirculate between blood and lymphoid organs
– Help to respond to antigens with T-cell help by
producing antibodies
– Half-life of approximately 4.5 months in periphery
Where do B-1 B cells develop from?
fetal liver to protect fetus from common microbial antigens
B-1 B cells constitute 30%-50% of B cells in what cavities of mice?
pleural and peritoneal
Describe B-1 B cell receptors:
-tend to bind microbial carbohydrate antigens
-bind with relatively low affinity
-similar to PRRs of innate immunity
B-1 B cells undergo apoptosis unless they interact with _______________
self-antigens
where are marginal zone cells found?
white pulp outer regions of the spleen
describe marginal zone cells:
-Appear to be specialized for blood-borne Ag recognition
-Recognize protein and carbohydrate antigens—similar to B-1
cells; Some may be able to do so without T-cell help
-Characterized by low levels of IgD and Fc receptor
-Seem to be derived from T2 cells with strong self-Ag signaling through BCR and binding of Notch ligands
What are the characteristics shared by B and T cell developmental pathways?
– Rearrangement of gene segments
– Screening processes to avoid self-reactivity
– Production of small subsets with discrete functions
– Production of larger “general purpose” subsets
What are the differences between B and T cell developmental pathways?
– Location of maturation and screening
– Screening processes used
* Positive and negative in T cells
* Negative in B cells
– Specific arrangements and identities of gene segments
recombined together
– Eventual outcomes of antigen receptor stimulation
* T cells require presentation and differentiate into helper or
killer subsets
* B cells require T-cell help and secrete antibodies
