PCB 3233 EXAM 5 QUESTIONS & ANSWERS
Know the different cells that can become plasma cells. - Answer --activated B cells
-isotype switched, somatically hyper mutated centrocytes
-memory B cells
What are the components of the B cell co-receptor ( CR2 is one of them) - Answer --
CR2: complement receptor-2: binds to complement deposited on the pathogen
-CD19: receptor signaling
-CD81/TAPA-1: binds to CD19 and is essential and bringing it to the B cell surface
What does CR1 do for the co-receptor - Answer -CR1 binding to C3b on a pathogen
facilitates the cleavage by factor I to ic3b and C3d, then the CR2 component of the B
cell co-receptor binds to C3d
What does TI antigen mean? What makes these different than TD antigens? - Answer -
-TI stands for Thymus Independent . They activate production of Cells without T
lymphocyte involvement
-TD antigens are Thymus Dependents AGs. Bulk of pathogens specific AB are
produced by TD AGs. TD AGs are activate B cells in the secondary typhoid tissues.
Describe B cell activation, CD40 ligand, CD40, NFkB, ICAM-1 and IL-4 secretion by T
cells. - Answer --Once B cells meet their antigen, the BCR and the co-receptor CXCL-
13 calls B cells to follicle. CCL-19/CCL-21 calls into the lymph nodes. These changes
TRAP the B cell in the Cell area close to the B cell zone. This allows for effector T-cells
to test their TCRs against the AG-MHC II on the B cell--> cognate interactions and
conjugate pairs.
-CD40 ligand expressed by T cells, to bind to CD40 on the B cell. Activates TF NFkB.
NFkB increases expression of adhesion molecule ICAM-1 to strengthen the adhesion
between the two cells.
-IL-4 is secreted by the T helper cells and allows for centrocyte differentiation into
memory B cells.
Define Follicular dendritic cells - Answer -FDC are non-lymphoid cells of follicles in
secondary lymphoid tissues. Their long branching points make contact with B cells-they
also have Fc and complement receptors that hold Ag":Ab complexes on their surfaces.
These cells are crucial in selecting Ag-binding B cells during Ab response.
Define dark zones in follicular dendritic cells - Answer -In the dark zones, there are
closely packed centroblasts and FDCs secrete those below for proliferation:
1. IL-6
2. IL-15
3. 8D6
4. BAFF
, Define light zones in follicular dendritic cells - Answer -In the light zones, slowly to non-
dividing centrocytes will interact with antigens held by FDC's
what is in each of the zones? - Answer --Dark zone: there are FDCs which secrete IL-6,
IL-5, 8D6, and BAFF to proliferate.
-close packed proliferating centroblasts and T cells
-T follicular helper cells attached to B -cells interacting with CD40 induce B cells to
make AID --> somatic hypermutation and biotype switching
What happens to the cells in the zones? - Answer --Centrocytes move from GC dark
zone-->capture antigen from FDC--> moves to GC light zone outer regions to helper T
cells
-In dark zones:
1. 80% centroblasts
2. Rapidly dividing activated B cells
3. Going through somatic hypermutation and isotope switching
4. No BCR on surface
5. B cells secrete AID
-In light zone: 10-20% centrocytes
a. slowly non-dividing B cells with mutated , isotope switched BCR
b. express BCR again to test against antigen
How do antibodies function? Do they destroy the pathogen directly or do they tag and
cover up things? - Answer -a. antibodies aim to neutralize the pathogen (doesn't
destroy)
b. activates complement via classical pathway
c.opsonization- tagging pathogens for phagocytosis
What is the B cells role in its activation? And what are the steps in B cell activation in
the lymph node. (Know steps) - Answer -a. Antigen binding (does the B cell take up the
antigen, what is this called)
i. Antigen binding (does the B cell take up the antigen, what is this called) TD antigen:
BCR signal + B cell coreceptor signal + TH2 signals (CD40:CD40L and cytokines); B
cell takes up TD antigen by receptor mediated endocytosis.
ii. TI-1 antigen: BCR signal + b cell coreceptor signal + antigen bound to additional
surface receptor
iii. TI-2 antigen: BCR signal + B cell coreceptor signal + extensive cross-linking caused
by repetitive epitopes on pathogen surface; results in early Ab response; limited, no
isotype switching, no hypermutation, no long-term memory.
iv. Binding of Ag sends a signal to the B cells nucleus to change gene expression. Yep,
the B cells take up the antigen by internalizing Ag by receptor mediated endocytosis
which processes and presents it to Th cells.
b. What are cognate interactions
Know the different cells that can become plasma cells. - Answer --activated B cells
-isotype switched, somatically hyper mutated centrocytes
-memory B cells
What are the components of the B cell co-receptor ( CR2 is one of them) - Answer --
CR2: complement receptor-2: binds to complement deposited on the pathogen
-CD19: receptor signaling
-CD81/TAPA-1: binds to CD19 and is essential and bringing it to the B cell surface
What does CR1 do for the co-receptor - Answer -CR1 binding to C3b on a pathogen
facilitates the cleavage by factor I to ic3b and C3d, then the CR2 component of the B
cell co-receptor binds to C3d
What does TI antigen mean? What makes these different than TD antigens? - Answer -
-TI stands for Thymus Independent . They activate production of Cells without T
lymphocyte involvement
-TD antigens are Thymus Dependents AGs. Bulk of pathogens specific AB are
produced by TD AGs. TD AGs are activate B cells in the secondary typhoid tissues.
Describe B cell activation, CD40 ligand, CD40, NFkB, ICAM-1 and IL-4 secretion by T
cells. - Answer --Once B cells meet their antigen, the BCR and the co-receptor CXCL-
13 calls B cells to follicle. CCL-19/CCL-21 calls into the lymph nodes. These changes
TRAP the B cell in the Cell area close to the B cell zone. This allows for effector T-cells
to test their TCRs against the AG-MHC II on the B cell--> cognate interactions and
conjugate pairs.
-CD40 ligand expressed by T cells, to bind to CD40 on the B cell. Activates TF NFkB.
NFkB increases expression of adhesion molecule ICAM-1 to strengthen the adhesion
between the two cells.
-IL-4 is secreted by the T helper cells and allows for centrocyte differentiation into
memory B cells.
Define Follicular dendritic cells - Answer -FDC are non-lymphoid cells of follicles in
secondary lymphoid tissues. Their long branching points make contact with B cells-they
also have Fc and complement receptors that hold Ag":Ab complexes on their surfaces.
These cells are crucial in selecting Ag-binding B cells during Ab response.
Define dark zones in follicular dendritic cells - Answer -In the dark zones, there are
closely packed centroblasts and FDCs secrete those below for proliferation:
1. IL-6
2. IL-15
3. 8D6
4. BAFF
, Define light zones in follicular dendritic cells - Answer -In the light zones, slowly to non-
dividing centrocytes will interact with antigens held by FDC's
what is in each of the zones? - Answer --Dark zone: there are FDCs which secrete IL-6,
IL-5, 8D6, and BAFF to proliferate.
-close packed proliferating centroblasts and T cells
-T follicular helper cells attached to B -cells interacting with CD40 induce B cells to
make AID --> somatic hypermutation and biotype switching
What happens to the cells in the zones? - Answer --Centrocytes move from GC dark
zone-->capture antigen from FDC--> moves to GC light zone outer regions to helper T
cells
-In dark zones:
1. 80% centroblasts
2. Rapidly dividing activated B cells
3. Going through somatic hypermutation and isotope switching
4. No BCR on surface
5. B cells secrete AID
-In light zone: 10-20% centrocytes
a. slowly non-dividing B cells with mutated , isotope switched BCR
b. express BCR again to test against antigen
How do antibodies function? Do they destroy the pathogen directly or do they tag and
cover up things? - Answer -a. antibodies aim to neutralize the pathogen (doesn't
destroy)
b. activates complement via classical pathway
c.opsonization- tagging pathogens for phagocytosis
What is the B cells role in its activation? And what are the steps in B cell activation in
the lymph node. (Know steps) - Answer -a. Antigen binding (does the B cell take up the
antigen, what is this called)
i. Antigen binding (does the B cell take up the antigen, what is this called) TD antigen:
BCR signal + B cell coreceptor signal + TH2 signals (CD40:CD40L and cytokines); B
cell takes up TD antigen by receptor mediated endocytosis.
ii. TI-1 antigen: BCR signal + b cell coreceptor signal + antigen bound to additional
surface receptor
iii. TI-2 antigen: BCR signal + B cell coreceptor signal + extensive cross-linking caused
by repetitive epitopes on pathogen surface; results in early Ab response; limited, no
isotype switching, no hypermutation, no long-term memory.
iv. Binding of Ag sends a signal to the B cells nucleus to change gene expression. Yep,
the B cells take up the antigen by internalizing Ag by receptor mediated endocytosis
which processes and presents it to Th cells.
b. What are cognate interactions
