BLD 434 EXAM 3 QUESTIONS AND ANSWERS WITH COMPLETE
SOLUTIONS GRADED A++
What is a characteristic of T independent antibody responses?
antibody produced is low affinity
Which Tfh cytokine would promote isotype switching to IgE by a B cell?
IL-4
What is the cytokine required to keep naive B cells alive, and thus to maintain the
pool of circulating naive B cells?
BAFF
Besides BCR binding of antigen, what other signal does a B cell require to stay
alive in a germinal center?
CD40L binding to CD40
Which of the B cell co-receptor complex proteins is a receptor for complement
C3D?
CD21
CR1
- present on macrophages
- binds the C3b fragment of complement deposited on a pathogen surface
- aids in phagocytosis of the pathogen
CR2
,CD21
- part of the B-cell co-receptor complex
- binds C3d and signals through CD19 to increase BCR signal 1000-10000-fold
Cognate Pairs
- a CD4 effector T cell bound via its antigen receptor to its target cell (either a
macrophage or a b cell)
ex: B cell and Tfh form a cognate pair to trigger isotype switching and somatic
hypermutation
DC
dendritic cell
- APC, stimulate T cells
- must activate naive T cell to Tfh
FDC
follicular dendritic cell
- holds antigen and provides cytokines to support B cell proliferation
Immune Complexes
Protein complex formed by the binding of antibodies to soluble antigens
- CD19, CD21, and CD81 form the B cell co-receptor complex
List the 3 CD proteins that form the B cell co-receptor complex, and their
functions
- CD19: signaling
- CD21: complement receptor
- CD81: adapter that holds the co-receptor complex
,T-dependent B lymphocyte antibody responses
- antigens refer to B cell antigens that require T cell help for proper response
- isotype switching and somatic hypermutation occur
- affinity maturation occurs
- memory response induced
T-independent B lymphocyte
- antigens cause B cell responses in the absence of T cell help
- Low affinity
- Minimal isotype switching - mostly IgM
- No somatic hypermutation
- no protective memory produced
List the Tfh cytokines and how they affect class-switching and the final fate of B
cells
T cell cytokines influence the isotype b cells switch to:
-- IFN-gamma: induces human B cells to switch to IgG1 (opsonizing)
-- IL-4 induces human b cells to switch to IgE
Cytokines modulate final fate of B cells:
-- IL-10 induces differentiation to plasma cell. causes activated B lymphocyte to isotype
switch to IgA
-- IL-4 induces memory B cell formation
List the 4 cell types that are minimally required to allow a T-dependent antibody
response to occur in a secondary lymphoid tissue and the relative physical
location of each cell
, - DC, B cell, Tfh (located in the T cell area)
- FDC (located in the germinal center)
Subcapsular Sinus Macrophages
- pick up antigen on CR2 and hold it for B cells to interrogate
FDC in filtering antigen from lymph fluid
- can hold antigen to primary follicle for B cells to interrogate
Medullary sinus macrophages
- highly phagocytic, clean efferent lymph entirely before it exits the lymph node. This
prevents the spread of infection downstream to blood stream
List the cells normally located in the dark zone, light zone, and mantle zone of a
germinal center
- Dark Zone: centroblasts
- Light Zone: centrocytes, FDC and Tfh
- Mantle Zone: low concentration of centrocytes
Important functions of FDC and it's ultimate affect on the immune system if FDC
were absent from secondary lymphoid tissues
- holds antigen and provide cytokines to support B cell proliferation
- Sustains B cell activation
- Hold antigen in primary follicle for B cells to interrogate
--- if absent, T cell dependent responses wouldn't occur
Identify the cytokine that is required for differentiation of FDC
FDC requires lymphotoxin (LT-alpha and LT-beta) as follicles will not form in the
absence of lymphotoxins.
SOLUTIONS GRADED A++
What is a characteristic of T independent antibody responses?
antibody produced is low affinity
Which Tfh cytokine would promote isotype switching to IgE by a B cell?
IL-4
What is the cytokine required to keep naive B cells alive, and thus to maintain the
pool of circulating naive B cells?
BAFF
Besides BCR binding of antigen, what other signal does a B cell require to stay
alive in a germinal center?
CD40L binding to CD40
Which of the B cell co-receptor complex proteins is a receptor for complement
C3D?
CD21
CR1
- present on macrophages
- binds the C3b fragment of complement deposited on a pathogen surface
- aids in phagocytosis of the pathogen
CR2
,CD21
- part of the B-cell co-receptor complex
- binds C3d and signals through CD19 to increase BCR signal 1000-10000-fold
Cognate Pairs
- a CD4 effector T cell bound via its antigen receptor to its target cell (either a
macrophage or a b cell)
ex: B cell and Tfh form a cognate pair to trigger isotype switching and somatic
hypermutation
DC
dendritic cell
- APC, stimulate T cells
- must activate naive T cell to Tfh
FDC
follicular dendritic cell
- holds antigen and provides cytokines to support B cell proliferation
Immune Complexes
Protein complex formed by the binding of antibodies to soluble antigens
- CD19, CD21, and CD81 form the B cell co-receptor complex
List the 3 CD proteins that form the B cell co-receptor complex, and their
functions
- CD19: signaling
- CD21: complement receptor
- CD81: adapter that holds the co-receptor complex
,T-dependent B lymphocyte antibody responses
- antigens refer to B cell antigens that require T cell help for proper response
- isotype switching and somatic hypermutation occur
- affinity maturation occurs
- memory response induced
T-independent B lymphocyte
- antigens cause B cell responses in the absence of T cell help
- Low affinity
- Minimal isotype switching - mostly IgM
- No somatic hypermutation
- no protective memory produced
List the Tfh cytokines and how they affect class-switching and the final fate of B
cells
T cell cytokines influence the isotype b cells switch to:
-- IFN-gamma: induces human B cells to switch to IgG1 (opsonizing)
-- IL-4 induces human b cells to switch to IgE
Cytokines modulate final fate of B cells:
-- IL-10 induces differentiation to plasma cell. causes activated B lymphocyte to isotype
switch to IgA
-- IL-4 induces memory B cell formation
List the 4 cell types that are minimally required to allow a T-dependent antibody
response to occur in a secondary lymphoid tissue and the relative physical
location of each cell
, - DC, B cell, Tfh (located in the T cell area)
- FDC (located in the germinal center)
Subcapsular Sinus Macrophages
- pick up antigen on CR2 and hold it for B cells to interrogate
FDC in filtering antigen from lymph fluid
- can hold antigen to primary follicle for B cells to interrogate
Medullary sinus macrophages
- highly phagocytic, clean efferent lymph entirely before it exits the lymph node. This
prevents the spread of infection downstream to blood stream
List the cells normally located in the dark zone, light zone, and mantle zone of a
germinal center
- Dark Zone: centroblasts
- Light Zone: centrocytes, FDC and Tfh
- Mantle Zone: low concentration of centrocytes
Important functions of FDC and it's ultimate affect on the immune system if FDC
were absent from secondary lymphoid tissues
- holds antigen and provide cytokines to support B cell proliferation
- Sustains B cell activation
- Hold antigen in primary follicle for B cells to interrogate
--- if absent, T cell dependent responses wouldn't occur
Identify the cytokine that is required for differentiation of FDC
FDC requires lymphotoxin (LT-alpha and LT-beta) as follicles will not form in the
absence of lymphotoxins.
