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Questions and Answers
What does somatic recombination within antigen receptor gene loci primarily contribute to?
What does somatic recombination within antigen receptor gene loci primarily contribute to?
- The deletion of self-reactive lymphocytes
- Receptor repertoire diversity (correct)
- The activation of effector cells
- The physical structure of lymphocytes
Which of the following best describes the process of negative selection in B cell development?
Which of the following best describes the process of negative selection in B cell development?
- Inactivation or deletion of lymphocytes with high affinity for self-antigens (correct)
- Expansion of lymphocytes with diverse antigen specificity
- Formation of memory B cells from activated lymphocytes
- Activation of lymphocytes in response to foreign antigens
Which of the following statements is NOT one of the major tenets of clonal selection theory?
Which of the following statements is NOT one of the major tenets of clonal selection theory?
- Antigen recognition leads to lymphocyte activation
- Effector cells share the receptor specificity of their parent lymphocyte
- Lymphocytes expand in response to their specific antigen
- Each lymphocyte expresses multiple antigen-specific receptors (correct)
In the context of B cell receptors (BCR), what is the role of heavy and light chains?
In the context of B cell receptors (BCR), what is the role of heavy and light chains?
What is the consequence of lymphocytes bearing receptors for self-molecules during the development process?
What is the consequence of lymphocytes bearing receptors for self-molecules during the development process?
What is the significance of having enough unique clones of lymphocytes?
What is the significance of having enough unique clones of lymphocytes?
How does clonal selection theory explain the memory of the adaptive immune system?
How does clonal selection theory explain the memory of the adaptive immune system?
What distinguishes the clonal structure of lymphocytes during their development?
What distinguishes the clonal structure of lymphocytes during their development?
Which of the following processes occurs independently in each B cell and contributes to receptor diversity?
Which of the following processes occurs independently in each B cell and contributes to receptor diversity?
Which statement accurately describes B cell antigen receptor assembly?
Which statement accurately describes B cell antigen receptor assembly?
What characterizes the configuration of the heavy (H) chain in B cell receptors?
What characterizes the configuration of the heavy (H) chain in B cell receptors?
During B cell development, what stage contributes to negative selection?
During B cell development, what stage contributes to negative selection?
What happens when a B cell binds a weak antigen post-bone marrow development?
What happens when a B cell binds a weak antigen post-bone marrow development?
What is the role of T cells in isotype switching for B cells?
What is the role of T cells in isotype switching for B cells?
Where does somatic hypermutation primarily occur?
Where does somatic hypermutation primarily occur?
What are complementarity determining regions (CDRs) significant for?
What are complementarity determining regions (CDRs) significant for?
Why is clonal selection important in B cell activation?
Why is clonal selection important in B cell activation?
What consequence does strong antigen binding have at the immature B cell stage?
What consequence does strong antigen binding have at the immature B cell stage?
How does isotype switching affect antibodies?
How does isotype switching affect antibodies?
What is the significance of the rearrangement of gene segments in B cell receptors?
What is the significance of the rearrangement of gene segments in B cell receptors?
Flashcards
Clonal Selection Theory
Clonal Selection Theory
A theory explaining adaptive immunity, stating that each lymphocyte has a unique antigen receptor, recognizing specific antigens. Activation leads to expansion of that specific lymphocyte clone.
Antigen-specific receptor
Antigen-specific receptor
A protein on the surface of a lymphocyte that specifically recognizes and binds to a particular antigen.
Lymphocyte activation
Lymphocyte activation
The process in which a lymphocyte is stimulated to proliferate and differentiate into effector cells, upon binding with an antigen.
Self Molecules
Self Molecules
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B cell receptor (BCR)
B cell receptor (BCR)
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B cell receptor gene loci
B cell receptor gene loci
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Somatic recombination
Somatic recombination
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Antigen-dependent steps
Antigen-dependent steps
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Antigen-independent steps
Antigen-independent steps
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Receptor repertoire
Receptor repertoire
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Germ-line gene configuration
Germ-line gene configuration
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BCR expression stages VDJ
BCR expression stages VDJ
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Clonal Selection Theory (Tenet 2)
Clonal Selection Theory (Tenet 2)
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Clonal Selection Theory (Tenet 3)
Clonal Selection Theory (Tenet 3)
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B cell negative selection
B cell negative selection
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Isotype switching
Isotype switching
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Somatic hypermutation
Somatic hypermutation
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Germinal centers
Germinal centers
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Antigen-dependent B cell development
Antigen-dependent B cell development
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T cell help
T cell help
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Study Notes
Clonal Selection Theory
- Each lymphocyte uniquely expresses a single antigen receptor with specific targeting. The complete repertoire of lymphocytes can respond to any antigen.
- Lymphocyte activation requires binding to an antigen.
- Activated lymphocytes' progeny (effector cells) express identical receptors as the parent cell.
- Lymphocytes with receptors for self-antigens are either inactivated or eliminated.
Clonal Selection Theory: Tenets 1, 2, & 3
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Tenet 1: Each lymphocyte is clonotypic, distinct from other cells except its immediate precursors or progeny. This is due to the antigen receptor and its genetic origin. Large diversity of lymphocytes is generated due to rearranged genes.
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Tenet 2, 3: Receptor binding is crucial for lymphocyte activation. BCRs (B cell receptors) on the cell surface act with signalling molecules that recognize when an antigen is bound and activate the cell. This leads to antibody production and the cell's proliferation and differentiation. The B cell's clone and antibody's specificity are fixed by the initial receptor-generating rearrangement.
B Cell Receptor (BCR) Structure
- BCR consists of heavy (H) and light (L) chains.
- One H chain locus and two L chain loci (k and l).
- The H chain has V, D, and J gene segments.
- The L chain has V and J gene segments.
- Only one L chain type (k or l) is expressed per cell.
- H and L chains join to form the receptor. Heavy chains initially associate with the more 5' C-region genes (µ and δ).
B Cell Development
- Antigen-independent: B cell development in the bone marrow, except for negative selection.
- Autoreactive B cells with strong self-antigen binding undergo apoptosis deletion.
- Weaker binding may result in anergy(non-responsiveness).
- Antigen-dependent: B cell development in the periphery.
- Antigen binding after leaving bone marrow can trigger IgM release.
- Isotype switching and somatic hypermutation require T cell help. Occurs in germinal centers within lymph nodes.
- Isotype switching: Altering antibody class (e.g., IgM to IgG) while maintaining the same antigen specificity. Crucial for different immune functions.
- Somatic hypermutation: Mutations improve antigen binding within the antibody's variable regions, concentrated in hypervariable regions (CDRs). This occurs concurrently with isotype switching.
- Germinal centers: Specialized areas in lymph nodes where B cell proliferation and maturation happen, along with isotype switching and somatic hypermutation, via T-cell interactions.
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