Title: Ch. 11. B Cell Generation, Activation, and
1Ch. 11. B Cell Generation, Activation, and
Differentiation B cells develop in the bone
marrow B cells undergo Ag-induced activation and
differentiation in the periphery Activated B
cells give rise to Ab-secreting plasma cells
and memory cells
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4Stages of B cell maturation are distinguished by
cell-surface markers
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8Why do only approx. 10 of B cells leave
the bone marrow? Negative selection of cells
that express Abs against self-antigens Cross-
linking of mIgM by self Ag may lead to cell
death or anergy Two kinds of Ags T-independent
(a few) dont need T cell help T-dependent (a
lot) need T cell help
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11B cell activation stimulates much
signal transduction Process has many parallels
to T cell activation
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17Initial exposure to antigen mIg has low
affinity Co-receptor may help with signaling
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23Where is the humoral response actually
induced? Lymphoid tissues concentrate
antigens Spleen from blood Lymph nodes - from
tissues Lots of APCs in lymph nodes dendritic
cells, macrophages
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27Generation of plasma cells Little membrane Ig
RNA processing supports secreted Ig Heavy and
light chain genes are transcribed at a higher
rate than in other cells Memory cells are
selected from a similar population of
high-affinity cells
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29Immune system may be nonresponsive (tolerant)
of antigen Antigen-mediated dosage competing
antigen previous exposure to one antigen may
suppress response to another Antibody-mediated p
reformed antibody can interfere
with immunization (by competing for
antigen?) Maternal Ab may interfere with
immunization
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31Summary of B cell maturation Antigen-independent
in bone marrow, antigen- dependent in
periphery TH cells are required for B cell
activation Affinity maturation, class switching
and formation of plasma and memory cells occur
in germinal centers Protective mechanisms such
as clonal anergy may prevent the formation of
self-reactive cells