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Questions and Answers
What are epitopes?
What are epitopes?
- Soluble proteins that inhibit immune responses.
- The primary source of antibodies produced by B-cells.
- Large molecules that incapacitate pathogens.
- Small molecular domains recognized by immune cells. (correct)
What characterizes an antigen?
What characterizes an antigen?
- It exclusively consists of DNA molecules.
- It is recognized by the cells of the adaptive immune system. (correct)
- It can only be a molecule found on the surface of pathogens.
- It triggers an immediate response without prior exposure.
Which immunoglobulin is described as the least abundant in plasma?
Which immunoglobulin is described as the least abundant in plasma?
- IgG
- IgA
- IgD (correct)
- IgM
What role do monomers of IgD serve in the immune system?
What role do monomers of IgD serve in the immune system?
What are the components that can serve as antigens?
What are the components that can serve as antigens?
What characterizes adaptive immunity in comparison to innate immunity?
What characterizes adaptive immunity in comparison to innate immunity?
Which cells become activated in adaptive immunity?
Which cells become activated in adaptive immunity?
What is the primary function of antigen presenting cells (APCs)?
What is the primary function of antigen presenting cells (APCs)?
Which organs are classified as primary lymphoid organs?
Which organs are classified as primary lymphoid organs?
What is the main role of secondary lymphoid organs?
What is the main role of secondary lymphoid organs?
Where is mucosa-associated lymphoid tissue (MALT) primarily located?
Where is mucosa-associated lymphoid tissue (MALT) primarily located?
What type of lymphocytes proliferate in the structures of MALT?
What type of lymphocytes proliferate in the structures of MALT?
How does the immune system primarily interconnect with the body's tissues?
How does the immune system primarily interconnect with the body's tissues?
What is the primary role of the Fc region of immunoglobulins?
What is the primary role of the Fc region of immunoglobulins?
What is the composition of the antigen-binding site of an antibody?
What is the composition of the antigen-binding site of an antibody?
Which part of the antibody molecule varies widely among different antibody molecules?
Which part of the antibody molecule varies widely among different antibody molecules?
What occurs to the DNA sequences coding for the antibody regions after B lymphocytes are activated?
What occurs to the DNA sequences coding for the antibody regions after B lymphocytes are activated?
How many identical light chains and heavy chains are found in antibodies?
How many identical light chains and heavy chains are found in antibodies?
What is the role of the variable region in immunoglobulins?
What is the role of the variable region in immunoglobulins?
Which of the following statements about immunoglobulins is false?
Which of the following statements about immunoglobulins is false?
What type of cells can produce and target with immunoglobulins aside from immune cells?
What type of cells can produce and target with immunoglobulins aside from immune cells?
What is the main function of thymic epithelial cells (TECs) in the thymus?
What is the main function of thymic epithelial cells (TECs) in the thymus?
Which type of TEC is characterized as squamous and forms a layer joined by desmosomes?
Which type of TEC is characterized as squamous and forms a layer joined by desmosomes?
What mainly defines the role of Hassall corpuscles in the thymus?
What mainly defines the role of Hassall corpuscles in the thymus?
During T-cell maturation in the thymus, what is the significance of the thymic microvasculature?
During T-cell maturation in the thymus, what is the significance of the thymic microvasculature?
What occurs during the differentiation of T lymphoblasts in the thymus?
What occurs during the differentiation of T lymphoblasts in the thymus?
Which of the following is NOT a characteristic of the thymus?
Which of the following is NOT a characteristic of the thymus?
What is the primary purpose of the thymus in the immune system?
What is the primary purpose of the thymus in the immune system?
Which process is primarily involved in the selective removal of T cells in the thymus?
Which process is primarily involved in the selective removal of T cells in the thymus?
What is the primary purpose of the two-stage selection process of thymocytes?
What is the primary purpose of the two-stage selection process of thymocytes?
During which stage do thymocytes first encounter MHC molecules?
During which stage do thymocytes first encounter MHC molecules?
What role do medullary thymic epithelial cells (TECs) play in negative selection?
What role do medullary thymic epithelial cells (TECs) play in negative selection?
What happens to T cells that strongly bind self-antigens during negative selection?
What happens to T cells that strongly bind self-antigens during negative selection?
Which type of T cells develops from thymocytes that interact with MHC class I molecules?
Which type of T cells develops from thymocytes that interact with MHC class I molecules?
What is the basis for central immunotolerance in the thymus?
What is the basis for central immunotolerance in the thymus?
What is the influence of cytokines from Hassall corpuscles in the thymic medulla?
What is the influence of cytokines from Hassall corpuscles in the thymic medulla?
How long does the selection process for thymocytes typically last?
How long does the selection process for thymocytes typically last?
Study Notes
Adaptive Immunity
- Provides specific and slower protection against invading microorganisms
- Involves B and T lymphocytes
- Activated by specific molecules from foreign cells presented by Antigen Presenting Cells (APCs)
- Memory lymphocytes produced for faster responses during repeat exposure
Immune System
- Provides defense against infections
- Composed of leukocytes in all tissues and lymphoid organs
- Connected through the blood and lymphatic circulation
Primary Lymphoid Organs
- Location of initial lymphocyte formation:
- Thymus
- Bone marrow
Secondary Lymphoid Organs
- Sites of lymphocyte activation and proliferation:
- Lymph nodes
- Spleen
- Peyer patches
- Appendix
Mucosa-Associated Lymphoid Tissue (MALT)
- Immune cells located throughout mucous membranes (digestive, respiratory, urogenital)
- Proliferating B lymphocytes form small, spherical lymphoid nodules
Immunoglobulins
- Multiple target cells and effects
- Common design:
- Two identical light chains and two identical heavy chains bound by disulfide bonds
- Fc region: constant carboxyl-terminal portion of heavy chains; recognized by basophil/mast cell receptors
- Variable region: first 110 amino acids; vary between antibody molecules
- Antigen-binding site: composed of variable sections of one heavy and one light chain; DNA sequences coding for these regions rearrange after B lymphocyte activation
Antigens & Antibodies
- Antigen: molecule recognized by adaptive immune cells, eliciting a response
- Epitopes: antigenic determinants; small molecular domains of an antigen recognized by immune cells
Antibodies
- Five classes:
- IgG: most common, crosses placenta, activates complement
- IgA: found in secretions, protects mucosal surfaces, prevents attachment of pathogens
- IgM: first antibody produced, activates complement, pentamer
- IgD: least abundant, bound to B lymphocytes, acts as antigen receptor
- IgE: involved in allergic reactions and parasitic infections
Thymus
- Primary lymphoid organ, site of T-lymphocyte differentiation and selection
- Removes T cells reacting to self-antigens, crucial for central tolerance
- 3 types of TECs in the cortex:
- Squamous TECs: form a layer lining the capsule and surrounding microvasculature; part of the blood-thymus barrier
- Subcapsular TECs: found beneath the capsule
- Cortical TECs: abundant in the cortex
- Medulla contains TECs, macrophages, and associated with unique epithelial cells (TECs)
- Hassall corpuscles: large aggregates of TECs, sometimes concentrically arranged, unique to the medulla
Role of Thymus in T-Cell Maturation & Selection
- T lymphoblasts: in the cortex, proliferate, recombine TCR genes, and express TCR, CD4, and CD8
- Selection process:
- Positive selection: TCRs must recognize and bind MHC molecules, occurs in the cortex
- Negative selection: removal of T cells strongly binding self-antigens, occurs in the medulla
- Aire gene: expressed by medullary TECs, promotes development of regulatory T cells
- T cell deletion and peripheral tolerance induced by regulatory T cells is the basis for central and peripheral immunotolerance
Spleen (Secondary Lymphoid Organ)
- Filters blood and removes old erythrocytes and platelets
- White pulp: rich in lymphocytes, containing central arteriole, PALS, and lymphatic nodules
- Red pulp: composed of cords and sinuses, involved in blood filtering and hemolysis
- Marginal zone: a transition zone containing macrophages and lymphocytes, important for antigen presentation
Lymph Nodes (Secondary Lymphoid Organ)
- Filters lymph and removes antigens
- Capsule: outer layer of connective tissue
- Subcapsular sinus: space underneath the capsule, filled with lymph
- Trabeculae: extensions of the capsule extending into the node
- Cortex: outer region containing follicles, a site of B lymphocyte proliferation
- Medulla: inner region containing cords of lymphoid cells, where B and T cells interact
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Description
Test your understanding of adaptive immunity and the immune system with this comprehensive quiz. Explore topics such as lymphocyte formation, the roles of primary and secondary lymphoid organs, and the functions of immunoglobulins. Perfect for biology students learning about human immunity.
