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Questions and Answers
What does clonal selection theory assert about lymphocytes?
What does clonal selection theory assert about lymphocytes?
Which process contributes to the repertoire diversity of B cell antigen receptors?
Which process contributes to the repertoire diversity of B cell antigen receptors?
Which of the following is true about effector cells derived from activated lymphocytes?
Which of the following is true about effector cells derived from activated lymphocytes?
What role does negative selection play in B cell development?
What role does negative selection play in B cell development?
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Which statement accurately describes the gene loci for B cell receptors?
Which statement accurately describes the gene loci for B cell receptors?
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What is the importance of receptor binding in lymphocyte activation?
What is the importance of receptor binding in lymphocyte activation?
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In the context of B cell development, what distinguishes antigen-dependent steps from antigen-independent steps?
In the context of B cell development, what distinguishes antigen-dependent steps from antigen-independent steps?
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How does the genetic process of somatic rearrangement contribute to B cell receptor diversity?
How does the genetic process of somatic rearrangement contribute to B cell receptor diversity?
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Which components make up the Heavy (H) chain of the B cell receptor?
Which components make up the Heavy (H) chain of the B cell receptor?
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What is the primary purpose of receptor binding in lymphocytes?
What is the primary purpose of receptor binding in lymphocytes?
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What happens during the negative selection step of B cell development?
What happens during the negative selection step of B cell development?
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Which of the following statements accurately describes antibody isotype switching?
Which of the following statements accurately describes antibody isotype switching?
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What is the role of somatic hypermutation in B cells?
What is the role of somatic hypermutation in B cells?
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In B cell receptor configuration, how many light chain types can be expressed?
In B cell receptor configuration, how many light chain types can be expressed?
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What is the primary function of the signaling complex associated with the B cell receptor?
What is the primary function of the signaling complex associated with the B cell receptor?
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Where does isotype switching and somatic hypermutation primarily occur?
Where does isotype switching and somatic hypermutation primarily occur?
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Study Notes
Clonal Selection Theory and B Cell Development
- Clonal selection theory explains the adaptive immune system's behavior
- Each lymphocyte has a unique antigen-specific receptor
- This receptor's binding is required for lymphocyte activation
- Effector cells have identical receptors to the parent cell
- Lymphocytes with receptors for self-molecules are inactivated or deleted
- B and T lymphocytes are clonotypic (unique)
- Diversity in antigen-specific receptors arises from somatic recombination (shuffling) in each cell
- This process creates a wider range of receptors than could be encoded in the genome, with progeny having identical receptors
B Cell Receptor Structure and Assembly
- B cell receptors (BCRs) are made of heavy (H) and light (L) chains
- One H chain locus and two L chain loci (kappa and lambda)
- Each locus contains multiple gene segments
- Germ-line gene configuration of Immunoglobin heavy- and light-chain loci
- H and L chains rearrange independently to form the receptor
- Initial expression involves the 5' most C region genes (e.g., IgM and IgD)
B Cell Receptor Expression
- Heavy (H) chains are formed from V, D, and J gene segments joined together
- Light (L) chains are formed from V and J gene segments joined to a C gene segment
- Both H and L chain rearrange independently and then pair
Clonal Selection Theory- Tenets 2 and 3
- Receptor binding is crucial for lymphocyte activation (recognition leads to action)
- BCRs are expressed on the cell surface together with non-polymorphic signaling molecules
- A signaling complex senses receptor binding and triggers intracellular activation
- Antibody production, proliferation, and differentiation occur
- B-cell clonotype and antibody specificity are determined by the genetic rearrangement of the receptor
Clonal Selection Theory- Tenet 4
- B cell development in bone marrow is mostly antigen-independent, except for negative selection
- Strong antigen binding at the immature B cell stage triggers apoptosis (deletion)
- Weaker binding can lead to anergy (unresponsiveness to antigen)
Antigen and T Cell-Dependent B Cell Development
- Antigen binding after leaving the bone marrow can cause the B cell to release IgM based on its cell surface receptor
- Isotype switching requires interaction with T cells ("T cell help")
- Isotype switching and somatic hypermutation occur in specialized germinal center structures in lymph nodes
Isotype Switching- Function
- Functionally, IgG, IgD, IgG1, IgG2, IgG3, IgG4, IgA, IgE are involved in neutralization, opsonization, etc.
- Distribution of the antibodies happens across different tissues (epithelial, placenta etc.)
Somatic Hypermutation- Antigen Binding
- Mutations within the H and L chain variable regions enhance antigen binding
- This process accumulates in "complementarity-determining regions (CDRs)" or "hypervariable" regions
- Occur in parallel to isotype switching
Isotype Switch and Somatic Hypermutation in Germinal Centers
- These processes occur within germinal centers within lymph nodes
- Proliferating B cells compete to present antigens and get T-cell help.
Summary of B Cell Development
- Somatic rearrangement is key to B cell receptor diversity
- Antigen-independent and antigen-dependent stages are involved in B cell development
- Some autoreactive B cells are deleted during the immature stage in the bone marrow
- Antigen binding triggers B cell activation
- Antibody specialization occurs through isotype switching and somatic hypermutation in germinal centers with T-cell help
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Description
This quiz explores the fundamentals of clonal selection theory and the development of B cells within the adaptive immune system. Learn about antigen-specific receptors, lymphocyte activation, and the unique composition of B cell receptors. Test your understanding of these crucial immunological concepts.
