39 Questions
What do B cells assemble in the bone marrow?
Cell surface forms of IgM monomer (sIgM) and IgD (sIgD) with the same antigen binding site
What are the 3 outcomes of B cells in the bone marrow that express sIgM and sIgD and recognize self-antigens?
Undergo apoptosis, undergo further DNA rearrangement of surface Ig, or migrate to the spleen and lymph nodes
What are the first 2 antibodies produced in an antibody response?
IgD and IgM
How are B lymphocytes in the spleen or lymph nodes activated?
Antigens are recognized by B cells on the surface of macrophages or follicular dendritic cells, and T helper cells provide signal 2 via CD154-CD40 interaction and cytokine secretion
What are the 3 outcomes of B cell proliferation?
Class switching, plasma cells, and memory B cells
What is class switching in B cells determined by, and what are the 3 responses?
Th1 cytokines (IL-4, IL-21) leading to IgG1 and IgG3, Th2 cytokines (IL-4) leading to IgE, and IL-21 leading to IgA
What cytokine can block IgA activation?
IL-4
What occurs simultaneously with class switching, and what enzyme initiates both processes?
Somatic hypermutation, and Activation Induced Cytidine Deaminase (AID)
Why is the secondary antibody response stronger than the primary response?
Due to affinity maturation caused by class switching and somatic hypermutation
What initiates somatic hypermutation in B cells?
Activation Induced Cytidine Deaminase (AID)
Which antibody class is activated by IL-21 cytokine?
IgA
What is the main function of AID in B cells?
Converting cytosine to uracil
Which outcome is a result of competition during somatic hypermutation?
Higher affinity plasma cells
What determines the specificity of IgG1 and IgG3 antibodies produced by B cells?
Th1 response
What is the main role of class switching in B cells?
Producing antibodies of different classes
Which response activates IgE antibodies in B cells?
Th2 response
What is the outcome of Th cell recognition of MHC II on B cells?
Induction of antibody production
How does the affinity maturation process affect B cell responses?
Results in stronger secondary responses
What process introduces point mutations in V region exons during RNA transcription in B cells?
Somatic hypermutation
What is the initial cell type that gives rise to B lymphocytes?
Pluripotent hematopoietic stem cell
What is the sequence of maturation stages for a B cell?
Pluripotent hematopoietic stem cell, common lymphoid progenitor, pro-B cell, mature naive B cell
Which region of an antibody is responsible for binding to antigens?
Fab region
What are the polypeptide components of an antibody?
2 identical heavy chains (Mr 50K) and 2 identical light chains (Mr 25K)
Which domains of an antibody form the binding site for antigens?
Adjacent N-terminal VL and VH domains
What is the primary function of antibodies?
Binding to infectious microorganisms and preventing infection
Which of the following is NOT a mechanism by which antibodies prevent infection?
Neutralizing toxins produced by microorganisms
What is the alternative name for antibodies?
Immunoglobulins
Where do B lymphocytes originate and mature?
Bone marrow
What is the role of the Fc region of an antibody?
Required for antibody function but does not bind antigens
What is the function of the flexible hinge region in antibodies?
It increases the ability of the antibody to bind to multiple epitopes on the same antigen.
What is the primary function of the heavy chain in antibodies?
Mediating effector functions such as complement activation and phagocytosis enhancement.
Which antibody class is primarily responsible for transplacental transport?
IgG
What is the primary function of IgE antibodies?
Degranulation of mast cells and eosinophils.
What is the primary location and function of IgA antibodies?
Mucosal surfaces, prevention of pathogen entry.
What is the primary mechanism that contributes to the diversity of antibodies?
Random recombination of gene segments.
What is the role of the Complementarity Determining Regions (CDRs) in antibodies?
They bind to specific epitopes on the antigen.
Which antibody class is primarily involved in signaling B cell activation?
IgD
What is the primary function of the Fc region in antibodies?
Mediating effector functions like complement activation and phagocytosis.
Which antibody class is primarily involved in the activation of the complement system?
IgM
Test your knowledge on B lymphocytes and antibodies with this quiz. From the origin and maturation of B lymphocytes to the functions of antibodies, this quiz covers key concepts in immunology.
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