B lymphocyte-mediate recognition of antigens and the immune response. Contents. B cell-mediate immune response to T-dependent antigen B cell-mediate immune response to T-independent antigen The general rule of humoral immune response. Humoral immunity:
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Humoral immunity: response
A immune response mediated by B lymphocyte-secreted antibodies. Its funtion is to neutralize and eliminate the antigens which induced the antibodies.
B cell-mediate recognition to TI antigens
TI-antigen: T-independent antigen
This type of antigen can activate B cells without the T cell help,
and most of them are bacterial polysaccharides and lipopolysaccharide.
1. TI-1 aitigen
2. TI-2 antigen
TI-1 antigen in high concentrations response
B-cell mediate recognition and immune response to TI-1 antigens
polyclonal B-cell activation
non-specific antibody response
TI-1 antigen in lower concentrations
Specific antibody response to TI-1 antigen
B cell-mediate recognition and immune response to TI-2 antigens
（二） response B cell-mediate recognition to TD antigens
二 response . Activation of B Cells
1）The specific antigenic recognition signal of B cell activation (first signal)
B cell coreceptor complex response
The first signal of B cell activation
2 response ）Costimulatory signal of B cell activation (second signal)
With the help of T cells
1.The activation of naïve Th cell
TCR presented on Th cells specifically recognizes and binds antigenic peptide-MHC-II complex displayed on B cell surface
The interaction of many adhesion molecular pairs makes the binding tighter.
☆ response Direct contact
T cells express CD40L，LFA-1，CD28, et al.
The most important molecule is CD40L(CD154)
B cell response
Presentation of antigen
Th cells can be induced to express many membranous molecules, for instance CD40L
The dark zone formation of the germinal center in lymph follicles
The clonal proliferation of B cells
B cells are differentiated to the cells in the germinal center
The formation of memory B cells
The function of cytokines response
IL-2, IFN- secreted by Th1 cells
IL-4、IL-5、IL-6 secreted by Th2 cells
TD antigen response
三 response . The signal transduction of B cell activation
（一）the antigen recognition structure of B cells
Signal transduction in B cells response
4. differentiation and maturation of B cells in the germinal center
Centroblasts germinal center
Blast proliferated B cells:
mantle zone formation
Non-proliferated B cells:
B cell activation and GC formation germinal center
(1) receptor editing germinal center
Further immunoglobulin gene rearrangement in seconary lymph organs---some potentially self-reactive B cells may be rescued.
Otherwise, self-reactive B cells undergo apoptosis or anergy.
(2) somatic hypermutation and germinal center
Ig+ B cells proliferate rapidly, and their already rearranged receptor genes undergo further diversification.
Some further diversifided Ig+ B cells acquir more affinitive BCR.
B cell maturation, migration and GC formation germinal center
B cell proliferation
antigen recognition and affinity maturation
no antigen loading B cells undergoing cell death
generation of plasma or memory B cells
B cell differentiation and maturation in germinal center
(3) immunoglobulin germinal centerclass switch
(4) destiny of maturated GC B cells germinal center
(6) Humoral immune response germinal center
Primary immune response germinal center
Antigen germinal center