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Clonal selection theory is a model that primarily explains the function of erythrocytes (red blood cells) in combating infections.
Answer: False
Explanation: Clonal selection theory explains the function of lymphocytes (B and T cells), not erythrocytes, in responding to specific antigens.
Clonal selection theory is a foundational concept for innate immunity rather than adaptive immunity.
Answer: False
Explanation: Clonal selection theory is the foundational concept for adaptive immunity, which involves learned responses to specific pathogens, not innate immunity.
According to clonal selection theory, a single lymphocyte can be activated by any antigen, irrespective of receptor specificity.
Answer: False
Explanation: A core tenet of the theory is that each lymphocyte has a unique receptor specificity; activation only occurs when an antigen matches that specific receptor.
A key tenet of clonal selection theory is that each lymphocyte possesses multiple receptor types with varying specificities.
Answer: False
Explanation: The theory posits that each lymphocyte possesses a single type of receptor with a unique, unchangeable specificity.
Clonal selection theory provides a foundational understanding of how the immune system recognizes and combats infections.
Answer: True
Explanation: The theory is a cornerstone of modern immunology, explaining the fundamental mechanisms by which lymphocytes respond to specific antigens to fight infections.
Clonal selection theory is now widely rejected by the scientific community in favor of more modern immunological models.
Answer: False
Explanation: Clonal selection theory remains the widely accepted model for describing how the adaptive immune system responds to infection and generates specificity.
What is the primary function of clonal selection theory within the field of immunology?
Answer: To explain how lymphocytes respond to specific antigens and combat infections.
Explanation: The theory provides a foundational model for how lymphocytes are selected and activated to respond to specific antigens, thereby explaining a core mechanism of the adaptive immune response.
What fundamental mechanism does clonal selection theory explain regarding antibodies?
Answer: The mechanism behind the generation of diverse antibody specificities.
Explanation: The theory's primary purpose was to clarify how the immune system can generate a vast and diverse repertoire of antibodies, each specific to a different pathogen.
Clonal selection theory is considered the foundational concept for which part of the immune system?
Answer: Adaptive immunity
Explanation: The theory is the foundational concept of adaptive immunity, which is characterized by its ability to learn and remember specific pathogens.
Which of the following is NOT one of the four main tenets summarizing clonal selection theory?
Answer: Lymphocytes with self-molecule receptors are encouraged to proliferate.
Explanation: A key tenet of the theory is that lymphocytes with receptors for self-molecules are destroyed or eliminated, not encouraged to proliferate, to prevent autoimmunity.
What is the current acceptance status of clonal selection theory within the scientific community?
Answer: It is a widely accepted model for describing immune responses.
Explanation: Clonal selection theory remains the widely accepted and foundational model for understanding how the adaptive immune system responds to infections.
Paul Ehrlich's 'side chain theory,' proposed in 1900, is classified as an instructive theory of antibody production.
Answer: False
Explanation: Ehrlich's theory was a selection theory, proposing that antigens select pre-existing 'side chains' (receptors). This was more accurate than the instructive theories that later became dominant for a time.
In his 1955 hypothesis, Niels Jerne proposed that soluble antibodies are only synthesized after an initial infection occurs.
Answer: False
Explanation: Jerne's hypothesis was that a vast array of soluble antibodies already exists in the blood serum prior to any infection, and an antigen selects a matching antibody from this pre-existing pool.
David W. Talmage's 1957 hypothesis differed from Ehrlich's by presuming each cell synthesized only one type of antibody.
Answer: True
Explanation: Talmage's key contribution was the presumption that each cell synthesizes only one type of antibody, which then proliferates upon antigen binding, a concept central to clonal selection.
Instructive theories of immunology posited that antigens functioned by selecting from a pool of pre-existing antibodies.
Answer: False
Explanation: Instructive theories proposed the opposite: that an antigen 'instructed' a cell on how to form a specific antibody. Selection theories, like Ehrlich's and Burnet's, proposed that antigens selected pre-existing specific cells or antibodies.
Jerne's 1955 hypothesis suggested that antibody selection occurred through cells phagocytosing immune complexes.
Answer: True
Explanation: Jerne's hypothesis stated that selection occurred when cells engulfed antigen-antibody complexes (phagocytosis) and then replicated the antibody structure.
Paul Ehrlich proposed his "side chain theory" of antibody production in what year?
Answer: 1900
Explanation: Paul Ehrlich proposed his influential "side chain theory," an early selection-based model of antibody production, in the year 1900.
How did Paul Ehrlich's "side chain theory" relate to later immunological theories?
Answer: It was a selection theory, more accurate than later instructive theories.
Explanation: Ehrlich's theory was a selection theory, positing that antigens select pre-existing receptors. This was conceptually more accurate than the instructive theories that temporarily dominated the field later.
What did Niels Jerne hypothesize in 1955 regarding soluble antibodies?
Answer: A vast array of them already exists in the blood serum before any infection.
Explanation: Jerne's 1955 hypothesis proposed that a vast repertoire of soluble antibodies exists in the serum prior to infection, and that an antigen selects a matching antibody from this pool.
What was the key distinction between David W. Talmage's 1957 hypothesis and Paul Ehrlich's theory?
Answer: Talmage proposed that each cell synthesized only one type of antibody.
Explanation: While both were selection theories, Talmage's critical contribution was the idea that each antibody-producing cell is monospecific, synthesizing only one type of antibody.
Niels Jerne's 1955 hypothesis suggested that the selection of antibodies occurred when certain cells performed what action?
Answer: Phagocytosed immune complexes.
Explanation: Jerne's hypothesis proposed a mechanism where cells would engulf antigen-antibody complexes (phagocytosis) and then replicate the antibody structure.
Which of the following best describes the "instructive theories" of immunology mentioned in the context of Paul Ehrlich's work?
Answer: They suggested that antigens somehow 'instructed' cells to produce specific antibodies.
Explanation: Instructive theories, which were contrasted with selection theories, proposed that an antigen acted as a template or guide that instructed a cell on how to synthesize a complementary antibody.
In 1957, Frank Macfarlane Burnet introduced the concept of clonal selection theory to explain the mechanism of antibody diversity.
Answer: True
Explanation: The Australian doctor Frank Macfarlane Burnet introduced the theory in 1957 to account for the extensive diversity of antibodies produced during an immune response.
Gustav Nossal and Joshua Lederberg provided the first experimental evidence for clonal selection theory in 1958 by showing a single B cell produces one antibody type.
Answer: True
Explanation: In 1958, Nossal and Lederberg provided direct experimental proof by demonstrating that a single B cell produces only one specific type of antibody.
Frank Macfarlane Burnet's seminal 1957 paper on clonal selection theory was first published in a prominent, mainstream immunology journal.
Answer: False
Explanation: Burnet's 1957 paper was published in the *Australian Journal of Science*, which was described as a rather obscure publication, not a prominent immunology journal.
Burnet formalized his clonal selection theory in 1959 with the publication of a research paper in the journal *Nature*.
Answer: False
Explanation: Burnet formalized his theory in 1959 with the publication of a book titled *The Clonal Selection Theory of Acquired Immunity*.
Burnet's hypothesis stated that each unique antibody pattern is the specific product of a distinct type of antigen.
Answer: False
Explanation: Burnet hypothesized that each unique antibody pattern is the specific product of a distinct clone of lymphocytes, not a type of antigen.
Frank Macfarlane Burnet's 1957 paper introducing his theory was titled 'The Clonal Selection Theory of Acquired Immunity.'
Answer: False
Explanation: Burnet's 1957 paper was titled 'A modification of Jerne's theory of antibody production using the concept of clonal selection.' His 1959 book was titled *The Clonal Selection Theory of Acquired Immunity*.
Who is credited with introducing the concept of clonal selection theory in 1957?
Answer: Frank Macfarlane Burnet
Explanation: The Australian doctor Frank Macfarlane Burnet is credited with introducing the theory in 1957 to explain the vast diversity of antibodies.
Who provided the first experimental evidence supporting clonal selection theory in 1958?
Answer: Gustav Nossal and Joshua Lederberg
Explanation: In 1958, Gustav Nossal and Joshua Lederberg confirmed a key prediction of the theory by demonstrating that a single B cell produces only one type of antibody.
In what publication did Frank Macfarlane Burnet first publish his paper on clonal selection theory in 1957?
Answer: *Australian Journal of Science*
Explanation: Burnet's initial 1957 paper on the theory was published in the *Australian Journal of Science*, which has been described as a relatively obscure publication for such a significant work.
When did Burnet further formalize his clonal selection theory with the publication of his book, *The Clonal Selection Theory of Acquired Immunity*?
Answer: 1959
Explanation: Two years after his initial paper, Burnet expanded upon and formalized his theory in his 1959 book, *The Clonal Selection Theory of Acquired Immunity*.
What did Gustav Nossal and Joshua Lederberg demonstrate in 1958 that supported clonal selection theory?
Answer: That a single B cell consistently produces only one type of antibody.
Explanation: Nossal and Lederberg's experiment provided direct evidence for the theory by showing that an individual B cell is monospecific, producing only one type of antibody.
What was the primary aim of Frank Macfarlane Burnet's work when he introduced clonal selection theory in 1957?
Answer: To clarify the extensive diversity of antibodies produced during an immune response.
Explanation: Burnet's work was specifically aimed at providing a clear theoretical framework to explain how the immune system is capable of producing such a vast and diverse array of specific antibodies.
As described by clonal selection theory, lymphocyte activation predominantly occurs in primary lymphoid organs such as the bone marrow.
Answer: False
Explanation: Lymphocyte activation primarily occurs in secondary lymphoid organs, such as the spleen and lymph nodes, not primary ones where they develop.
The unique specificity of lymphocyte receptors is generated through a process called V(D)J recombination.
Answer: True
Explanation: The vast diversity and unique specificity of lymphocyte receptors are generated through a genetic process known as V(D)J recombination.
For a lymphocyte to become activated, it must undergo self-replication prior to encountering a corresponding antigen.
Answer: False
Explanation: Activation requires the binding of a specific antigen to the lymphocyte's receptor; proliferation (self-replication) occurs after this activation event, not before.
When an antigen enters the body, it attaches to any available lymphocyte, which triggers a general proliferation of all lymphocyte clones.
Answer: False
Explanation: An antigen attaches only to lymphocytes carrying a specific, corresponding receptor, which then initiates the preferential proliferation of only that matching clone.
The descendant cells of an activated lymphocyte can produce new lymphocytes but are incapable of liberating soluble antibodies.
Answer: False
Explanation: The descendants of activated lymphocytes are capable of both producing new lymphocytes and actively liberating soluble antibodies.
The diagram illustrating clonal selection theory depicts all immature lymphocytes maturing into active forms, regardless of antigen binding.
Answer: False
Explanation: The diagram shows that most inactive lymphocytes never encounter a matching antigen and remain dormant. Only those that bind a specific foreign antigen become activated.
The diagram of clonal selection theory illustrates hematopoietic stem cells differentiating directly into mature, active lymphocytes.
Answer: False
Explanation: The diagram shows a multi-step process: hematopoietic stem cells differentiate into immature lymphocytes, which then mature into inactive forms before any potential activation.
In which type of lymphoid organs does the activation of lymphocytes primarily occur, according to clonal selection theory?
Answer: Secondary lymphoid organs such as the spleen and lymph nodes.
Explanation: While lymphocytes develop in primary lymphoid organs, their activation by antigens primarily takes place in secondary lymphoid organs, which are specialized sites for initiating immune responses.
According to clonal selection theory, what is required for a lymphocyte to become activated?
Answer: Occupation of its specific receptor by an antigen.
Explanation: A core tenet of the theory is that lymphocyte activation is initiated by the binding of a specific antigen to the cell's unique surface receptor.
According to Burnet's hypothesis, what happens when an antigen enters the body and attaches to a lymphocyte?
Answer: The cell is activated, initiating preferential proliferation of matching clones.
Explanation: The binding of an antigen to its corresponding lymphocyte receptor serves as the activation signal, which then triggers the cell to multiply and create a large population of identical clones.
What capabilities do the descendants of activated lymphocytes possess?
Answer: They are capable of actively liberating soluble antibodies and producing new lymphocytes.
Explanation: The clonal descendants of an activated lymphocyte differentiate into effector cells that can secrete antibodies and also into memory cells that can produce new lymphocytes upon re-exposure.
How is the unique specificity of lymphocyte receptors generated according to clonal selection theory?
Answer: Via a process called V(D)J recombination.
Explanation: The vast diversity of lymphocyte receptors is generated by a process of genetic rearrangement known as V(D)J recombination during lymphocyte development.
According to the theory, what happens when a specific antigen activates a lymphocyte?
Answer: The activated cell multiplies, generating identical clones.
Explanation: Upon activation by a specific antigen, the selected lymphocyte undergoes rapid cell division (proliferation) to create a large population of identical clones to fight the infection.
What is the process by which immature lymphocytes develop diverse antigen receptors, as depicted in the clonal selection theory diagram?
Answer: Genetic rearrangement
Explanation: The diagram shows that the vast diversity of antigen receptors is created through a process of genetic rearrangement (like V(D)J recombination) during lymphocyte differentiation.
To ensure a robust immune response, lymphocytes bearing receptors for the body's own molecules are permitted to mature fully.
Answer: False
Explanation: A critical aspect of the theory is that lymphocytes reactive to self-molecules are destroyed at an early developmental stage to prevent autoimmunity.
Immunological memory, according to Burnet's clonal selection theory, involves the cloning of two types of lymphocytes: one for immediate action and one for long-term immunity.
Answer: True
Explanation: Burnet's theory accounted for immunological memory by proposing the generation of two lymphocyte clones: one for immediate action against the pathogen and another, longer-lasting clone to provide future immunity.
Clonal selection theory explains that all lymphocytes, including those reactive to self-antigens, survive the embryonic stage to ensure a diverse immune repertoire.
Answer: False
Explanation: The theory posits that lymphocytes reactive to self-tissue are eliminated during embryonic development to establish self-tolerance.
What happens to lymphocytes that bear receptors for the body's own self-molecules, according to clonal selection theory?
Answer: They are destroyed at an early developmental stage.
Explanation: To prevent autoimmunity, lymphocytes that carry receptors for self-molecules are eliminated during their development, a process known as negative selection.
How did Burnet's clonal selection theory explain immunological memory?
Answer: By explaining the cloning of two types of lymphocytes: immediate and longer-lasting.
Explanation: The theory accounts for memory by proposing that an activated lymphocyte produces two types of clones: short-lived effector cells for the immediate infection and long-lived memory cells for future immunity.
The diagram illustrating clonal selection theory shows that immature lymphocytes with receptors binding to what are destroyed?
Answer: Antigens from the body's own tissues
Explanation: The diagram illustrates the principle of self-tolerance, where lymphocytes that bind to the body's own antigens (self-antigens) are eliminated to prevent autoimmune reactions.
Burnet and Peter Medawar collaborated on understanding immunological tolerance, a phenomenon explained by clonal selection.
Answer: True
Explanation: Burnet and Medawar's collaboration on immunological tolerance was a key application and extension of the principles outlined in clonal selection theory.
In 1959, Burnet's work led him to propose that tissue transplantation between foreign recipients was generally impossible due to immune rejection.
Answer: False
Explanation: Burnet's 1959 proposal was groundbreaking because it suggested that, under certain circumstances, tissues could be successfully transplanted into foreign recipients, advancing the field significantly.
Burnet and Medawar received the Nobel Prize in Physiology or Medicine in 1960 for their work on immunological tolerance and tissue transplantation.
Answer: True
Explanation: Burnet and Medawar were jointly awarded the 1960 Nobel Prize in Physiology or Medicine for their discoveries concerning acquired immunological tolerance and its application to tissue transplantation.
Niels Kaj Jerne's immune network theory, proposed in 1974, is a concept entirely separate from and unrelated to clonal selection theory.
Answer: False
Explanation: Jerne's immune network theory is not separate from clonal selection; rather, it is firmly based on the foundational concepts of clonal selection.
Niels Kaj Jerne won the Nobel Prize in Physiology or Medicine in 1984 for his contributions to the immune network theory.
Answer: True
Explanation: Jerne was awarded the Nobel Prize in Physiology or Medicine in 1984, largely in recognition of his influential immune network theory.
What phenomenon did Burnet and Peter Medawar collaborate on understanding, which is also explained by clonal selection?
Answer: Immunological tolerance
Explanation: Burnet and Medawar's Nobel Prize-winning work focused on acquired immunological tolerance, the process by which the immune system learns to not attack certain antigens, a concept explained by the clonal deletion of self-reactive cells.
In what year did Burnet and Medawar share the Nobel Prize in Physiology or Medicine?
Answer: 1960
Explanation: For their groundbreaking work on immunological tolerance and its implications for tissue transplantation, Burnet and Medawar were jointly awarded the Nobel Prize in Physiology or Medicine in 1960.
What theory did Niels Kaj Jerne propose in 1974, which is firmly based on clonal selection?
Answer: The immune network theory
Explanation: In 1974, Niels Kaj Jerne proposed the immune network theory, which describes the immune system as a regulated network. This theory is built upon the foundational principles of clonal selection.
What recognition did Niels Kaj Jerne receive in 1984 for his contributions to immunology?
Answer: The Nobel Prize in Physiology or Medicine
Explanation: For his significant contributions to immunology, including the immune network theory, Niels Kaj Jerne was awarded the Nobel Prize in Physiology or Medicine in 1984.
What significant proposal did Burnet make in 1959 that advanced the field of tissue transplantation?
Answer: That tissues could be successfully transplanted into foreign recipients under certain circumstances.
Explanation: Based on his work on immunological tolerance, Burnet proposed that it was possible to transplant tissues into foreign recipients under specific conditions, a major step forward for the field.