BLD434 EXAM3 QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS GRADED A++
1) Define the following terms [including what cell(s) the term applies to, as
appropriate]:
CR1, CR2, cognate pairs, DC, FDC, and immune complex(es).
CR1: receptor for complement that helps to target C3b cleavage by Factor I
CR2: aka CD21 is a receptor for complement that is part of the B cell co-receptor
Cognate pairs: formed by antigen-activated B cells that Tfh. Is the same thing as linked
recognition in which the Tfh helps activate the B cell. The cognate pair is absolutely
essential. By forming cognate pair, isotype switching and somatic hyper-mutation are
triggered.
DC: Dendritic cell but activate naïve T cell to Tfh (activation step)
FDC: Follicular Dendritic Cells hold antigen and provide cytokines to support B cell
proliferation.
Immune complex - Protein complex formed by binding of antigens to soluble antibodies.
,2) List the 3 CD proteins that form the B cell co-receptor complex, and the
functions of each of the proteins (if known).
CD19: signals to increase BCR signal 1,000 to 10,000 fold
CD21/CR2: Binds C3d
CD81: adapter protein that holds the complex to the BCR during activation
List the TFH cytokines and how they affect class-switching and the final fate of B
cells.
IFNy and IL-4 influence isotype switch
- IFNy induces human B cells to switch to IgG1 (opsonizing)
- IL-4 induces human B cells to switch to IgE
IL-10 and IL-4 modulate the final fate of B cells
- IL-10 induces differentiation into plasma cells
- 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 within the secondary lymphoid tissue.
• Dendritic Cell T cell zone
• Tfh T cell zone
• B cell primary lymphoid follicle
• FDC located in primary lymphoid follicle
,• There are two activation steps that occur simultaneously: DC must activate naïve T
cell to Tfh AND B cell is activated by antigen
• FDC holds antigen in place and provides cytokines to support B cell proliferation (in
order to maintain activation)
• B cell and Tfh form cognate pair to trigger isotype switching and somatic hyper-
mutation
• B cell undergoes affinity maturation by competing for antigen on the FDC
Describe the role of subcapsular sinus macrophages, FDC, and medullary sinus
macrophages in filtering antigen from lymph fluid.
The subscapular sinus macrophages pick up antigen on CR2 and hold it for B cells to
interrogate
FDC can hold antigen in primary follicle for B cells to interrogate
Medullary sinus macrophages are highly phagocytic and clean the efferent lymph
entirely before it exits the LN. This prevents the spread of infection downstream
List the cell(s) that are normally located in the dark zone, light zone and mantle
zone of a germinal center (include centroblasts, centrocytes, FDC and T helper
cells in your list).
Dark zone: centroblasts
Light zone: centrocytes, FDC, T helper cells
Mantle zone: naïve mature B cells (not yet activated)
, Identify as many important functions of FDC as you can, and predict the ultimate
effect on the immune system if FDC were absent from secondary lymphoid
tissues.
Functions:
• Provides survival signal for B cell to keep them alive (BAFF)
• Hold antigen and provide cytokines that support B cell proliferation
• Sustains B cell activation
• Filtering antigen from lymph fluid
• Holds antigen in primary follicle for B cells to interrogate
• Germinal centers home around FDC networks
There would be no B cell circulation/B cell immunity as B cells would not be activated
nor would they stay alive when they are not activated by antigen.
Identify the cytokine that is required for differentiation of FDC.
LT-alpha and beta
(lymphotoxin)
Explain the 2 signals a B cell requires in a germinal center to maintain activation,
and the consequence if it does not receive these signals.
• Binding of antigen held on the FDC
• Linked recognition/cognate pair: antigen is processed and presented by the B cell to
the Tfh that provides second signal through CD40L and CD40
COMPLETE SOLUTIONS GRADED A++
1) Define the following terms [including what cell(s) the term applies to, as
appropriate]:
CR1, CR2, cognate pairs, DC, FDC, and immune complex(es).
CR1: receptor for complement that helps to target C3b cleavage by Factor I
CR2: aka CD21 is a receptor for complement that is part of the B cell co-receptor
Cognate pairs: formed by antigen-activated B cells that Tfh. Is the same thing as linked
recognition in which the Tfh helps activate the B cell. The cognate pair is absolutely
essential. By forming cognate pair, isotype switching and somatic hyper-mutation are
triggered.
DC: Dendritic cell but activate naïve T cell to Tfh (activation step)
FDC: Follicular Dendritic Cells hold antigen and provide cytokines to support B cell
proliferation.
Immune complex - Protein complex formed by binding of antigens to soluble antibodies.
,2) List the 3 CD proteins that form the B cell co-receptor complex, and the
functions of each of the proteins (if known).
CD19: signals to increase BCR signal 1,000 to 10,000 fold
CD21/CR2: Binds C3d
CD81: adapter protein that holds the complex to the BCR during activation
List the TFH cytokines and how they affect class-switching and the final fate of B
cells.
IFNy and IL-4 influence isotype switch
- IFNy induces human B cells to switch to IgG1 (opsonizing)
- IL-4 induces human B cells to switch to IgE
IL-10 and IL-4 modulate the final fate of B cells
- IL-10 induces differentiation into plasma cells
- 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 within the secondary lymphoid tissue.
• Dendritic Cell T cell zone
• Tfh T cell zone
• B cell primary lymphoid follicle
• FDC located in primary lymphoid follicle
,• There are two activation steps that occur simultaneously: DC must activate naïve T
cell to Tfh AND B cell is activated by antigen
• FDC holds antigen in place and provides cytokines to support B cell proliferation (in
order to maintain activation)
• B cell and Tfh form cognate pair to trigger isotype switching and somatic hyper-
mutation
• B cell undergoes affinity maturation by competing for antigen on the FDC
Describe the role of subcapsular sinus macrophages, FDC, and medullary sinus
macrophages in filtering antigen from lymph fluid.
The subscapular sinus macrophages pick up antigen on CR2 and hold it for B cells to
interrogate
FDC can hold antigen in primary follicle for B cells to interrogate
Medullary sinus macrophages are highly phagocytic and clean the efferent lymph
entirely before it exits the LN. This prevents the spread of infection downstream
List the cell(s) that are normally located in the dark zone, light zone and mantle
zone of a germinal center (include centroblasts, centrocytes, FDC and T helper
cells in your list).
Dark zone: centroblasts
Light zone: centrocytes, FDC, T helper cells
Mantle zone: naïve mature B cells (not yet activated)
, Identify as many important functions of FDC as you can, and predict the ultimate
effect on the immune system if FDC were absent from secondary lymphoid
tissues.
Functions:
• Provides survival signal for B cell to keep them alive (BAFF)
• Hold antigen and provide cytokines that support B cell proliferation
• Sustains B cell activation
• Filtering antigen from lymph fluid
• Holds antigen in primary follicle for B cells to interrogate
• Germinal centers home around FDC networks
There would be no B cell circulation/B cell immunity as B cells would not be activated
nor would they stay alive when they are not activated by antigen.
Identify the cytokine that is required for differentiation of FDC.
LT-alpha and beta
(lymphotoxin)
Explain the 2 signals a B cell requires in a germinal center to maintain activation,
and the consequence if it does not receive these signals.
• Binding of antigen held on the FDC
• Linked recognition/cognate pair: antigen is processed and presented by the B cell to
the Tfh that provides second signal through CD40L and CD40
