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B cell subsets
Mature B cells
Fetal liver stem cells …….B-1 B cell
 Bone marrow stem cells…..B-2 B cells….marginal zone B
cells and follicular B cells with Both IgM & IgD
 B-1 B cells (CD5+)
found in peritoneum and mucosal sites
Limited diversity
Secrete IgM
 Marginal zone B cells
Located in the spleen
Express IgM and CD21
Respond to blood-borne microbes
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B cell surface markers
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B cell receptor(Ag recognition)
CD19 (B cell activation)
CD21or CR2 (B cell activation and EBV receptor)
CD25 (binds IL- 2)
CD27 (memory B cells )
CD40 (B cell activation)
CD80 or B7(costimulator for T cell activation)
CD81 (B cell activation)
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CD19 is one of the most reliable surface biomarker for B cells
It is expressed from pre-B cells until the terminal
differentiation to plasma cells.
CD19 expression in mature B cells are 3-fold higher than that
found in immature B cells, with slightly higher expression in
B1 cells than in B2 cells
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CD19 acts as a critical co-receptor for BCR signal transduction
The CD19 gene encodes a cell surface molecule that assembles
with the antigen receptor of B lymphocytes in order to
decrease the threshold for antigen receptor-dependent
stimulation
It primarily acts as a B cell co-receptor in conjunction with
CD21 and CD81
B regulatory cells
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The hallmark of an effective immune response is
inflammation.
After infection, the inflammatory response is critical for
clearing pathogens and initiating wound healing
If unresolved, this inflammatory response causes injury to host
tissues, which can lead to the development of a wide variety of
immune-mediated pathologies in cascades that control wound
healing
Directly, cognate interactions between Breg cells and T cells
are thought to control Treg cell induction, given that B cells
deficient in major histocompatibility complex
class II and B7 do not exhibit regulatory function).
Indirectly,Breg cells suppress the differentiation of T helper 1
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plasmablasts can also suppress inflammatory responses
supports the proposal that any B cell has the potential to
differentiate into a Breg cell
it has now been demonstrated that immature B cells, mature B
cells, and plasmablasts all have the capacity to differentiate
into IL-10-producing Breg cells in both mice and humans.
This supports the concept that the primary requisite for Breg
cell differentiation is not the expression of a Breg-cell-specific
lineage factor but rather the environment in which a B cell
finds itself.
Toll-like receptor (TLR) and/or CD40 activation is the most
well-characterized signal known to induce their differentiation
pro-inflammatory cytokines can also drive the induction of IL-