71 Questions
What are the three broad stages involved in the production of plasma cells and memory B cells?
Maturation, Activation, Differentiation
Which stage involves the interaction of mature B cells with antigens?
Activation
which of the following is correct three broad stages Production of plasma cells and memory B cells ?
All of the above
Which stage involves the development of immunocompetent B cells?
Maturation
What is the outcome of the antigen-independent maturation phase of B-cell development?
leave the bone marrow and Mature B cells circulating in the blood and lymph
What happens to naive B cells in the periphery if they do not encounter soluble protein antigen and activated TH cells?
They die within a few days
What is affinity maturation of B-cell development?
A+C
What happens if a B cell is activated by an antigen specific to its membrane-bound antibody?
The specific antigen
Naive B cells in the periphery can survive for a long time even without encountering soluble protein antigen and activated TH cells.
False
Only about 10% of potential B cells reach maturity and exit the bone marrow during B-cell development.
True
Where do Pro-B cells proliferate?
Bone marrow
What is the role of IL-7 in B cell development?
Promotes heavy chain rearrangement
What is necessary for a B cell to become fully functional?
Expression of both IgM and IgD on membrane
What type of antigens require B cell activation, proliferation, and differentiation in the periphery?
A+B
Which of the following is correct B-cell Activation and Proliferation?
A+B
What type of antigen requires B cell direct contact with TH cells for activation?
Thymus-dependent (TD) antigens
What type of antigen elicits a T-independent response and binds to both Ig and innate receptors on B cells?
Multivalent antigens
At high antigen concentrations, what is the outcome of mitogenic stimulation for all B cells bearing the relevant innate receptors?
Elicit a polyclonal, antibody-secreting response
What is the characteristic of the antibodies produced when B-cell stimulation occurs through the innate receptor only?
Only a small minority of the antibodies produced will be able to bind directly to the TI-1 antigen
What is the term used for antigens that bind to both Ig and innate receptors on B cells and elicit a T-independent response?
T independent (TI) antigens
What is the characteristic of Type 2 thymus-independent (TI-2) antigens?
They are highly multivalent and bind only to Ig receptors
What is the ability of TI-2 antigens to activate B cells in the absence of T-cell help attributed to?
Their remarkably multivalent array of antigenic determinants
What is the additional characteristic of most naturally occurring TI-2 antigens?
They have the ability to bind complement fragments C3d
What is the outcome of mitogenic stimulation for all B cells bearing the relevant innate receptors at high antigen concentrations?
They do not elicit a polyclonal response
What is required for signal transduction by an activated B-cell receptor?
Antigen crosslinkage of the BCR
What must membrane Ig be associated with to generate a signal for B-cell activation?
Ig-α/Ig-β
Which components interact with the immunoreceptor tyrosine-based activation motifs (ITAMs) after antigen crosslinkage of the BCR?
Members of the Src family of tyrosine kinases
Why are the cytoplasmic tails of membrane-bound antibodies too short to generate a signal for B-cell activation?
They are too short to associate with tyrosine kinases and G proteins
Membrane Ig must be associated with B-cell receptor Ig-α/Ig-β for the initial stages of signal transduction by an activated B-cell receptor (BCR).
True
The cytoplasmic tails of membrane-bound antibodies are long enough to generate a signal by associating with tyrosine kinases and G proteins.
False
Following antigen crosslinkage of the BCR, the immunoreceptor tyrosine-based activation motifs (ITAMs) interact with members of the Src family of tyrosine kinases, activating the kinases.
True
Only about 50% of potential B cells reach maturity and exit the bone marrow during B-cell development.
False
Where do small foci of proliferating B cells form after antigen-mediated B-cell activation takes place?
At the edges of the T-cell–rich zone
What is the outcome of the activated B cells with Th cells leaving the foci to the primary follicles?
Formation of memory B cells
What happens to all the activated cells after they migrate to the center of secondary follicles?
They form the germinal center
Where does antigenic challenge leading to a humoral immune response involve a complex series of events?
Lymph nodes
What is formed at the edges of the T-cell–rich zone after antigen-mediated B-cell activation takes place?
Small foci of proliferating B cells
What happens to the activated B cells with Th cells after they develop into memory B cells?
They differentiate into IgM and IgG isotypes
What are the three important B-cell differentiation events that take place in germinal centers?
Affinity maturation, class switching, formation of plasma and memory B cells
When do germinal centers arise after initial exposure to thymus-dependent antigen?
Within 7-10 days
What happens during the first stage of germinal-center formation?
Activated B cells undergo intense proliferation
What occurs in the antigen-dependent phase of B-cell development?
Affinity maturation and class switching
What is the outcome of B cells migrating into germinal centers?
Rapid cell division and mutation of rearranged immunoglobulin V region genes within the dark zone
What characterizes centrocytes within the light zone of germinal centers?
Increased expression of surface Ig
What must centrocytes do within the light zone to survive?
Interact with follicular dendritic cells and T helper cells
What do centrocytes compete with each other to bind within the light zone?
Antigen
What happens to B cells that fail antigen-mediated selection within germinal centers?
They die by apoptosis.
What is the major outcome of the germinal center in the context of B cell development?
Generation of higher affinity B cells from lower affinity B cells.
What is the outcome of the encounter with TH cells for B cells within germinal centers?
Class switching.
What is the fate of B cells bearing high-affinity membrane immunoglobulin within germinal centers?
They differentiate into memory B cells.
What is the role of CD40L in class switching?
It is essential for the induction of class switching
What is the outcome of X-linked hyper-IgM syndrome?
Patients produce IgM but not other isotypes
What is the consequence of TH cells failing to express CD40L?
Patients fail to generate memory cell populations
What is the significance of cytokines in class switching?
They are required for B cells to switch from IgM to other isotypes
Class switching involves the change in the isotype of the antibody produced by the B cell.
True
Affinity maturation is the decrease in the average affinity of the antibodies produced during B-cell activation.
False
Thymus-dependent antigens require B cell direct contact with TH cells for activation.
True
Naive B cells in the periphery can survive for a long time even without encountering soluble protein antigen and activated TH cells.
True
What characterizes a primary response to antigen in the humoral immune system?
A lag phase and subsequent clonal expansion
What is the role of memory B cells?
Stop dividing and enter the G0 phase of the cell cycle
What is the outcome of the activation of memory cells by antigen?
Secondary antibody response
What distinguishes a secondary antibody response from a primary response?
Several distinguishing features from the primary response
Why are certain vaccines for measles and mumps not administered to infants before the age of 1 year?
The maternal IgG acquired by the fetus suppresses the humoral response to the vaccines
What is the impact of immunizing an infant with measles or mumps vaccine while maternal antibody is still present?
It results in a low humoral response and inadequate production of memory cells
What is the reason behind not administering certain vaccines to infants before the age of 1 year?
The vaccines have been found to be ineffective in eliciting an immune response in infants below the age of 1 year
What is the consequence of maternal IgG acquired by the fetus on the immunization of infants with specific vaccines?
It suppresses the humoral response, causing inadequate production of memory cells
What is the state of unresponsiveness called when the immune system encounters an antigen?
Immune tolerance
What plays an important role in the regulation of the immune effector response?
Antigenic competition
What can render an animal tolerant or result in the formation of memory cells upon a previous encounter with antigen?
Antigenic competition
Which components must be regulated heavily in the immune effector response?
Humoral and cell-mediated branches
What does a B cell differentiate into after undergoing clonal expansion?
Antibody-secreting plasma cells and memory B cells.
Test your knowledge of the stages involved in B-cell development, activation, differentiation, and the humoral immune response. This quiz covers the generation of mature B cells, their activation upon antigen interaction, and the subsequent differentiation into plasma cells and memory B cells.
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