Podcast
Questions and Answers
Cells at this point are both CD4 positive and CD8 positive.
Cells at this point are both CD4 positive and CD8 positive.
True
MHC in the thymus only expresses foreign peptide during negative selection.
MHC in the thymus only expresses foreign peptide during negative selection.
False
Negative selection occurs early in T cell development.
Negative selection occurs early in T cell development.
True
The TCR binds tightly to self-peptide, leading to T cell survival.
The TCR binds tightly to self-peptide, leading to T cell survival.
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Co-receptors CD4 and CD8 are important for T cell recognition of MHC.
Co-receptors CD4 and CD8 are important for T cell recognition of MHC.
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CD4 and CD8 are types of co-receptors in T cells.
CD4 and CD8 are types of co-receptors in T cells.
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Positive selection in T cell development occurs when T cells fail to recognize MHC.
Positive selection in T cell development occurs when T cells fail to recognize MHC.
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Immature T cells receive signals to survive during negative selection.
Immature T cells receive signals to survive during negative selection.
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Depending on the interaction with MHC class I or class II, T cells can differentiate into either CD4 or CD8 cells.
Depending on the interaction with MHC class I or class II, T cells can differentiate into either CD4 or CD8 cells.
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Dendritic cells present MHC to T cells during their development.
Dendritic cells present MHC to T cells during their development.
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Checkpoints during T cell development help in selecting appropriate T cells.
Checkpoints during T cell development help in selecting appropriate T cells.
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CD4 positive T cells are responsible for presenting antigens to other immune cells.
CD4 positive T cells are responsible for presenting antigens to other immune cells.
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The term 'Cluster of Differentiation' refers to various surface proteins on T cells.
The term 'Cluster of Differentiation' refers to various surface proteins on T cells.
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T cell development occurs in the Thymus.
T cell development occurs in the Thymus.
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CD8+ T cells are also known as Helper T cells.
CD8+ T cells are also known as Helper T cells.
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T cell activation takes place in the Peripheral Tissue.
T cell activation takes place in the Peripheral Tissue.
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Immature T cells are exposed to antigens in the Thymus.
Immature T cells are exposed to antigens in the Thymus.
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CD4+ T cells provide help to B cells and macrophages.
CD4+ T cells provide help to B cells and macrophages.
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The life cycle of a T cell includes an effector function.
The life cycle of a T cell includes an effector function.
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T cell function is limited to initial antigen exposure.
T cell function is limited to initial antigen exposure.
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Antigen exposure occurs after T cell development.
Antigen exposure occurs after T cell development.
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T cells can act in any peripheral tissue.
T cells can act in any peripheral tissue.
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The response to recognized antigens leads to antibody production.
The response to recognized antigens leads to antibody production.
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T cells are part of the adaptive immune system and respond specifically to antigens.
T cells are part of the adaptive immune system and respond specifically to antigens.
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The primary function of Helper T cells is to directly kill infected cells.
The primary function of Helper T cells is to directly kill infected cells.
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Cytotoxic T cells are responsible for killing cells infected with intracellular pathogens.
Cytotoxic T cells are responsible for killing cells infected with intracellular pathogens.
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MHC class I molecules present antigens to T helper cells.
MHC class I molecules present antigens to T helper cells.
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Each T cell has a unique T cell receptor (TCR) that recognizes specific antigens.
Each T cell has a unique T cell receptor (TCR) that recognizes specific antigens.
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T cells are able to activate their response without any interaction with other cells.
T cells are able to activate their response without any interaction with other cells.
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Negative selection is a process that involves eliminating T cells that do not react strongly with self-antigens.
Negative selection is a process that involves eliminating T cells that do not react strongly with self-antigens.
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Positive selection ensures that T cells can recognize foreign antigens effectively.
Positive selection ensures that T cells can recognize foreign antigens effectively.
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T helper cells can be categorized into Th1, Th2, Th17, and Treg subsets.
T helper cells can be categorized into Th1, Th2, Th17, and Treg subsets.
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Memory T cells have a short lifespan of up to 5 years.
Memory T cells have a short lifespan of up to 5 years.
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Cytokines play no role in the immune response.
Cytokines play no role in the immune response.
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The process of clonal expansion occurs after T cells are activated.
The process of clonal expansion occurs after T cells are activated.
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Peripheral tolerance is unrelated to T cell regulation.
Peripheral tolerance is unrelated to T cell regulation.
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Diseases related to T cell deficiencies can arise from improper development or function of T cells.
Diseases related to T cell deficiencies can arise from improper development or function of T cells.
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Central tolerance occurs in the thymus and eliminates most auto-reactive T cells.
Central tolerance occurs in the thymus and eliminates most auto-reactive T cells.
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Peripheral tolerance eliminates T cells that recognize self-antigens not expressed in the thymus.
Peripheral tolerance eliminates T cells that recognize self-antigens not expressed in the thymus.
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Autoimmunity occurs when auto-reactive T cells fail to recognize self-antigens.
Autoimmunity occurs when auto-reactive T cells fail to recognize self-antigens.
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DiGeorge syndrome is caused by a deletion on chromosome 21.
DiGeorge syndrome is caused by a deletion on chromosome 21.
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Individuals with DiGeorge syndrome have a small or absent thymus, resulting in poor T cell production.
Individuals with DiGeorge syndrome have a small or absent thymus, resulting in poor T cell production.
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DiGeorge syndrome is associated with increased susceptibility to recurrent infections.
DiGeorge syndrome is associated with increased susceptibility to recurrent infections.
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Autoimmune disorders include conditions such as diabetes and hypertension.
Autoimmune disorders include conditions such as diabetes and hypertension.
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IL-5 is involved in activating mast cells for allergic responses.
IL-5 is involved in activating mast cells for allergic responses.
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Peripheral tolerance is only relevant to the thymus.
Peripheral tolerance is only relevant to the thymus.
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All T helper cells can activate B cells to produce antibodies.
All T helper cells can activate B cells to produce antibodies.
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Th17 cells primarily produce IL-4.
Th17 cells primarily produce IL-4.
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Regulatory T cells (Treg) produce IL-10 to help switch off Th responses.
Regulatory T cells (Treg) produce IL-10 to help switch off Th responses.
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Cytotoxic T lymphocytes (CTL) target free pathogens directly.
Cytotoxic T lymphocytes (CTL) target free pathogens directly.
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Virally infected cells display antigens on MHC class II molecules.
Virally infected cells display antigens on MHC class II molecules.
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Perforin helps destroy infected cells by forming pores in their membranes.
Perforin helps destroy infected cells by forming pores in their membranes.
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Granzymes are enzymes that promote necrosis in infected cells.
Granzymes are enzymes that promote necrosis in infected cells.
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VDJ recombination results in the generation of unique TCRs with different specificities.
VDJ recombination results in the generation of unique TCRs with different specificities.
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Once a TCR is rearranged, it can be altered again during the T cell's life.
Once a TCR is rearranged, it can be altered again during the T cell's life.
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T cell development includes a stage where immature T cells undergo checkpoints to verify TCR presence.
T cell development includes a stage where immature T cells undergo checkpoints to verify TCR presence.
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TCR gene rearrangement can result in approximately $10^{14}$ different receptor combinations.
TCR gene rearrangement can result in approximately $10^{14}$ different receptor combinations.
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All T cells are equipped with co-receptors that allow them to recognize MHC molecules.
All T cells are equipped with co-receptors that allow them to recognize MHC molecules.
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The TCR has a single antigen specificity that is determined during T cell development.
The TCR has a single antigen specificity that is determined during T cell development.
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DiGeorge syndrome is associated with a complete absence of T cells due to thymic failure.
DiGeorge syndrome is associated with a complete absence of T cells due to thymic failure.
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Positive selection eliminates T cells that strongly bind self-antigens during development.
Positive selection eliminates T cells that strongly bind self-antigens during development.
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Positive selection in T cell development retains T cells that do not recognize MHC.
Positive selection in T cell development retains T cells that do not recognize MHC.
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CD4 and CD8 co-receptors are essential for T cell recognition of MHC molecules.
CD4 and CD8 co-receptors are essential for T cell recognition of MHC molecules.
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Immature T cells are negatively selected when they bind strongly to self-antigens.
Immature T cells are negatively selected when they bind strongly to self-antigens.
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The TCR interacts only with MHC class I molecules during T cell development.
The TCR interacts only with MHC class I molecules during T cell development.
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Checkpoints in T cell development ensure the selection of appropriate T cells.
Checkpoints in T cell development ensure the selection of appropriate T cells.
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CD8 positive T cells primarily recognize MHC class II molecules.
CD8 positive T cells primarily recognize MHC class II molecules.
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T cell development occurs exclusively outside the thymus.
T cell development occurs exclusively outside the thymus.
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Dendritic cells present MHC molecules to help in the positive selection of T cells.
Dendritic cells present MHC molecules to help in the positive selection of T cells.
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Positive selection in T cell development occurs when T cells can effectively recognize MHC.
Positive selection in T cell development occurs when T cells can effectively recognize MHC.
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Naïve T cells are only weakly reactive to self-antigens during negative selection.
Naïve T cells are only weakly reactive to self-antigens during negative selection.
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During T cell development, only CD4 positive cells can be generated during positive selection.
During T cell development, only CD4 positive cells can be generated during positive selection.
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The primary role of CD4 T cells is to directly kill infected cells.
The primary role of CD4 T cells is to directly kill infected cells.
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Checkpoints in T cell development are used to ensure the selection of appropriate T cells.
Checkpoints in T cell development are used to ensure the selection of appropriate T cells.
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Only double positive T cells can recognize MHC during the positive selection process.
Only double positive T cells can recognize MHC during the positive selection process.
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Negative selection eliminates T cells that recognize self-antigens strongly.
Negative selection eliminates T cells that recognize self-antigens strongly.
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T cell activation occurs mainly in the spleen.
T cell activation occurs mainly in the spleen.
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MHC molecules only present foreign antigens during T cell development.
MHC molecules only present foreign antigens during T cell development.
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Naive T cells have already met their specific antigen before activation.
Naive T cells have already met their specific antigen before activation.
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A T cell undergoes clonal expansion after its TCR recognizes an antigen.
A T cell undergoes clonal expansion after its TCR recognizes an antigen.
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Three signals are required for the activation of Naive T cells.
Three signals are required for the activation of Naive T cells.
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Effector T cells remain within the lymph nodes to perform their functions.
Effector T cells remain within the lymph nodes to perform their functions.
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Dendritic cells present MHC to T cells primarily during their maturation in the thymus.
Dendritic cells present MHC to T cells primarily during their maturation in the thymus.
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Naive T cells travel to the peripheral tissues to encounter their specific antigens.
Naive T cells travel to the peripheral tissues to encounter their specific antigens.
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Each T cell has a unique T cell receptor (TCR) that allows it to recognize multiple antigens.
Each T cell has a unique T cell receptor (TCR) that allows it to recognize multiple antigens.
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Central tolerance occurs primarily in the peripheral tissues.
Central tolerance occurs primarily in the peripheral tissues.
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Peripheral tolerance specifically targets T cells that recognize self-antigens not present in the thymus.
Peripheral tolerance specifically targets T cells that recognize self-antigens not present in the thymus.
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DiGeorge syndrome is caused by a deletion on chromosome 22, leading to a small thymus.
DiGeorge syndrome is caused by a deletion on chromosome 22, leading to a small thymus.
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Autoimmune disorders can arise when auto-reactive T cells fail to recognize self-antigens.
Autoimmune disorders can arise when auto-reactive T cells fail to recognize self-antigens.
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Individuals with DiGeorge syndrome are at increased risk for recurrent infections due to excessive T cell production.
Individuals with DiGeorge syndrome are at increased risk for recurrent infections due to excessive T cell production.
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The concept of tolerance includes both central and peripheral mechanisms.
The concept of tolerance includes both central and peripheral mechanisms.
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Autoimmunity can be triggered by a complete absence of T cells in the body.
Autoimmunity can be triggered by a complete absence of T cells in the body.
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Negative selection ensures the survival of T cells that strongly bind to self-antigens.
Negative selection ensures the survival of T cells that strongly bind to self-antigens.
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Antigen is the first signal required for T cell activation.
Antigen is the first signal required for T cell activation.
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CD4 co-receptors interact with MHC class I molecules.
CD4 co-receptors interact with MHC class I molecules.
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Costimulatory receptors such as B7 are expressed by dendritic cells in the absence of microbes.
Costimulatory receptors such as B7 are expressed by dendritic cells in the absence of microbes.
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Instructive cytokines help differentiate CD4+ T cell subsets.
Instructive cytokines help differentiate CD4+ T cell subsets.
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IL-4 stimulates the Th1 subset of CD4+ T cells.
IL-4 stimulates the Th1 subset of CD4+ T cells.
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Activated APCs produce cytokines that aid in the differentiation of naïve T cells.
Activated APCs produce cytokines that aid in the differentiation of naïve T cells.
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Co-stimulation is not necessary for the activation of T cells.
Co-stimulation is not necessary for the activation of T cells.
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The only signal needed for T cell activation is the interaction between TCR and antigen.
The only signal needed for T cell activation is the interaction between TCR and antigen.
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Costimulatory signals enhance the T cell proliferation process.
Costimulatory signals enhance the T cell proliferation process.
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Th1 cells primarily respond to helminth infections.
Th1 cells primarily respond to helminth infections.
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Cytokines direct different CD4+ T cell subsets by providing specific signals.
Cytokines direct different CD4+ T cell subsets by providing specific signals.
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Dendritic cells have no role in T cell activation.
Dendritic cells have no role in T cell activation.
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CD28 is a receptor found on the surface of dendritic cells.
CD28 is a receptor found on the surface of dendritic cells.
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MHC molecules are essential for T cells to recognize foreign antigens.
MHC molecules are essential for T cells to recognize foreign antigens.
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All T cells require instructive cytokines for complete activation.
All T cells require instructive cytokines for complete activation.
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The constant region of T cell receptors changes depending on the T cell clone.
The constant region of T cell receptors changes depending on the T cell clone.
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Positive selection in T cell development occurs in the peripheral tissues.
Positive selection in T cell development occurs in the peripheral tissues.
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The majority of thymocytes die because they do not successfully undergo positive selection.
The majority of thymocytes die because they do not successfully undergo positive selection.
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T cell receptors have both variable and constant regions that are specifically designed for interaction with antigens and self-antigens.
T cell receptors have both variable and constant regions that are specifically designed for interaction with antigens and self-antigens.
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Thymocytes that recognize self-antigens are positively selected for maturation.
Thymocytes that recognize self-antigens are positively selected for maturation.
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All T cell clones have the same T cell receptor (TCR).
All T cell clones have the same T cell receptor (TCR).
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The variable region of the T cell receptor is responsible for its antigen-binding specificity.
The variable region of the T cell receptor is responsible for its antigen-binding specificity.
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Immature T cells that do not recognize any MHC molecules are eliminated during the selection process.
Immature T cells that do not recognize any MHC molecules are eliminated during the selection process.
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VDJ recombination allows for the creation of $10^{14}$ different T cell receptors with unique specificities.
VDJ recombination allows for the creation of $10^{14}$ different T cell receptors with unique specificities.
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Once a TCR gene is rearranged, it can be altered to create additional unique receptors later in the T cell's life.
Once a TCR gene is rearranged, it can be altered to create additional unique receptors later in the T cell's life.
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Checkpoints during T cell development ensure that T cells are eliminated if they do not have a TCR.
Checkpoints during T cell development ensure that T cells are eliminated if they do not have a TCR.
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Positive selection in T cell development occurs when T cells strongly recognize self-MHC molecules.
Positive selection in T cell development occurs when T cells strongly recognize self-MHC molecules.
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Immature T cells are selected based on their ability to interact with any antigen presented in the Thymus.
Immature T cells are selected based on their ability to interact with any antigen presented in the Thymus.
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T cells proliferate and differentiate in the presence of foreign antigens after their development.
T cells proliferate and differentiate in the presence of foreign antigens after their development.
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DiGeorge syndrome is characterized by normal T cell production and function despite the absence of a thymus.
DiGeorge syndrome is characterized by normal T cell production and function despite the absence of a thymus.
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APC stands for Antigen Producing Cell.
APC stands for Antigen Producing Cell.
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TCR stands for T Cell Recognition.
TCR stands for T Cell Recognition.
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Orderly removal of auto-reactive T cells occurs in the thymus through central tolerance mechanisms.
Orderly removal of auto-reactive T cells occurs in the thymus through central tolerance mechanisms.
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All non-nucleated cells can present antigens to T cells via MHC class I.
All non-nucleated cells can present antigens to T cells via MHC class I.
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Cytotoxic T cells have CD4 co-receptors.
Cytotoxic T cells have CD4 co-receptors.
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Macrophages can function as antigen presenting cells.
Macrophages can function as antigen presenting cells.
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Dendritic cells are only involved in presenting antigens during positive selection.
Dendritic cells are only involved in presenting antigens during positive selection.
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Cytotoxic T cells predominantly function in recognizing and responding to antigens presented by MHC class II molecules.
Cytotoxic T cells predominantly function in recognizing and responding to antigens presented by MHC class II molecules.
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Memory T cells have a lifespan of several years to help the body respond to previously encountered antigens.
Memory T cells have a lifespan of several years to help the body respond to previously encountered antigens.
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CD4+ T cells are crucial in aiding B cells and macrophages after initial antigen exposure.
CD4+ T cells are crucial in aiding B cells and macrophages after initial antigen exposure.
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Cytotoxic T cells, also known as CD4+ T cells, are primarily involved in directly killing infected cells.
Cytotoxic T cells, also known as CD4+ T cells, are primarily involved in directly killing infected cells.
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Immature T cells are developed solely in the lymph nodes before exposure to any antigens.
Immature T cells are developed solely in the lymph nodes before exposure to any antigens.
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T cell activation occurs in the secondary lymphoid tissue, such as lymph nodes.
T cell activation occurs in the secondary lymphoid tissue, such as lymph nodes.
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Positive selection allows T cells that cannot recognize MHC to develop further into functional cells.
Positive selection allows T cells that cannot recognize MHC to develop further into functional cells.
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T cell responses can occur only in specific tissues rather than peripheral tissues.
T cell responses can occur only in specific tissues rather than peripheral tissues.
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Regulatory T cells (Treg) primarily function to enhance the responses of other T cells.
Regulatory T cells (Treg) primarily function to enhance the responses of other T cells.
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Autoimmunity arises when T cells successfully recognize and attack self-antigens.
Autoimmunity arises when T cells successfully recognize and attack self-antigens.
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CD8+ T cells aid in the production of antibodies during an immune response.
CD8+ T cells aid in the production of antibodies during an immune response.
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The life cycle of a T cell includes an effector function that occurs after antigen recognition.
The life cycle of a T cell includes an effector function that occurs after antigen recognition.
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Individuals with DiGeorge syndrome have a normal thymus and produce T cells effectively.
Individuals with DiGeorge syndrome have a normal thymus and produce T cells effectively.
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Peripheral tolerance is responsible for eliminating T cells that recognize self-antigens not expressed in the thymus.
Peripheral tolerance is responsible for eliminating T cells that recognize self-antigens not expressed in the thymus.
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Autoimmune disorders can occur when auto-reactive T cells successfully recognize self-antigens.
Autoimmune disorders can occur when auto-reactive T cells successfully recognize self-antigens.
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Central tolerance occurs exclusively outside the thymus and involves the deletion of auto-reactive T cells.
Central tolerance occurs exclusively outside the thymus and involves the deletion of auto-reactive T cells.
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T cell immunodeficiencies like DiGeorge syndrome can lead to increased susceptibility to infections across multiple organ systems.
T cell immunodeficiencies like DiGeorge syndrome can lead to increased susceptibility to infections across multiple organ systems.
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All forms of tolerance, including central and peripheral, aim to promote auto-reactive T cell activity.
All forms of tolerance, including central and peripheral, aim to promote auto-reactive T cell activity.
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Multiple sclerosis and rheumatoid arthritis are examples of conditions that can result from the failure of T cell tolerance.
Multiple sclerosis and rheumatoid arthritis are examples of conditions that can result from the failure of T cell tolerance.
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Negative selection is the process through which T cells that strongly react to self-antigens are selected for survival.
Negative selection is the process through which T cells that strongly react to self-antigens are selected for survival.
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Severe Combined Immunodeficiency (SCID) is characterized by low or absent T and B cells, making it typically fatal in the first two years of life.
Severe Combined Immunodeficiency (SCID) is characterized by low or absent T and B cells, making it typically fatal in the first two years of life.
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X-linked severe SCID is the least common form of SCID.
X-linked severe SCID is the least common form of SCID.
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Effector T cells can be differentiated into CD4 and CD8 lineages after clonal expansion.
Effector T cells can be differentiated into CD4 and CD8 lineages after clonal expansion.
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Hypocalcaemia is a common symptom associated with X-linked severe SCID.
Hypocalcaemia is a common symptom associated with X-linked severe SCID.
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Naïve T cells become effector cells after they are activated in the thymus.
Naïve T cells become effector cells after they are activated in the thymus.
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CD8+ T cells are also known as cytotoxic T cells, responsible for killing cells infected by pathogens.
CD8+ T cells are also known as cytotoxic T cells, responsible for killing cells infected by pathogens.
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The thymus is primarily a site for mature T cell function, not for T cell development.
The thymus is primarily a site for mature T cell function, not for T cell development.
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Learning difficulties and psychiatric issues are sometimes associated with congenital heart problems.
Learning difficulties and psychiatric issues are sometimes associated with congenital heart problems.
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Helper T cells primarily kill infected cells as their main function.
Helper T cells primarily kill infected cells as their main function.
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TCR rearrangement occurs during the early stages of T cell maturation in the thymus.
TCR rearrangement occurs during the early stages of T cell maturation in the thymus.
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VDJ recombination generates TCRs with a maximum of $10^{14}$ unique specificities.
VDJ recombination generates TCRs with a maximum of $10^{14}$ unique specificities.
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Once a TCR is rearranged, it can still be modified to change specificity later in the T cell's life.
Once a TCR is rearranged, it can still be modified to change specificity later in the T cell's life.
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The development of T cells takes place primarily in the bone marrow.
The development of T cells takes place primarily in the bone marrow.
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Checkpoints during T cell development are designed to select appropriate TCRs.
Checkpoints during T cell development are designed to select appropriate TCRs.
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T cells express multiple TCRs to increase their chance of recognizing various antigens.
T cells express multiple TCRs to increase their chance of recognizing various antigens.
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Immature T cells can have altered TCRs during the selection process.
Immature T cells can have altered TCRs during the selection process.
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T cell checkpoints include assessments to determine if a T cell has an effective TCR.
T cell checkpoints include assessments to determine if a T cell has an effective TCR.
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The random rearrangement of TCR genes does not ensure a diverse T cell repertoire.
The random rearrangement of TCR genes does not ensure a diverse T cell repertoire.
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CD4 and CD8 are exclusively found on mature T cells.
CD4 and CD8 are exclusively found on mature T cells.
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Positive selection of T cells occurs when they fail to recognize MHC molecules.
Positive selection of T cells occurs when they fail to recognize MHC molecules.
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Negative selection predominantly removes T cells that react too weakly to self-antigens.
Negative selection predominantly removes T cells that react too weakly to self-antigens.
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T cell activation requires a single signal for the naive T cell to differentiate into an effector T cell.
T cell activation requires a single signal for the naive T cell to differentiate into an effector T cell.
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Immature T cells interact with dendritic cells to develop positively by recognizing MHC.
Immature T cells interact with dendritic cells to develop positively by recognizing MHC.
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Naive T cells are cells that have previously encountered their specific antigen.
Naive T cells are cells that have previously encountered their specific antigen.
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CD8 T cells are typically responsible for assisting B cells in antibody production.
CD8 T cells are typically responsible for assisting B cells in antibody production.
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During T cell activation, the T cell receptor (TCR) is critical for recognizing antigen bound to MHC on dendritic cells.
During T cell activation, the T cell receptor (TCR) is critical for recognizing antigen bound to MHC on dendritic cells.
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All T cells recognize any antigen presented on MHC molecules without specificity.
All T cells recognize any antigen presented on MHC molecules without specificity.
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The interaction between TCR and MHC is necessary for T cell activation to occur.
The interaction between TCR and MHC is necessary for T cell activation to occur.
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Checkpoints in T cell development serve to eliminate all self-reactive T cells.
Checkpoints in T cell development serve to eliminate all self-reactive T cells.
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The presence of co-receptors CD4 and CD8 does not influence the type of T cell developed.
The presence of co-receptors CD4 and CD8 does not influence the type of T cell developed.
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Clonal expansion occurs when a specific T cell clone proliferates after recognizing its antigen.
Clonal expansion occurs when a specific T cell clone proliferates after recognizing its antigen.
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Naive T cells can differentiate into memory T cells without prior activation.
Naive T cells can differentiate into memory T cells without prior activation.
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Dendritic cells play a crucial role in T cell activation by presenting antigens in lymph nodes.
Dendritic cells play a crucial role in T cell activation by presenting antigens in lymph nodes.
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Cytotoxic T cells are also known as killer T cells because they kill infected or altered cells.
Cytotoxic T cells are also known as killer T cells because they kill infected or altered cells.
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T helper cells primarily produce cytokines that activate eosinophils and facilitate responses against intracellular pathogens.
T helper cells primarily produce cytokines that activate eosinophils and facilitate responses against intracellular pathogens.
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IL-12 and IFN-γ are associated with the activation of Th2 cells.
IL-12 and IFN-γ are associated with the activation of Th2 cells.
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Memory T cells have a longer lifespan than effector T cells, allowing for quicker responses upon re-exposure to the same antigen.
Memory T cells have a longer lifespan than effector T cells, allowing for quicker responses upon re-exposure to the same antigen.
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Th17 cells are primarily known for producing IL-5, which is involved in activating mast cells.
Th17 cells are primarily known for producing IL-5, which is involved in activating mast cells.
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Cytotoxic T cells are also known as CD4+ T cells.
Cytotoxic T cells are also known as CD4+ T cells.
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Positive selection ensures T cells can recognize both self and foreign antigens effectively.
Positive selection ensures T cells can recognize both self and foreign antigens effectively.
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Helper T cells provide assistance primarily to B cells and cytotoxic T cells.
Helper T cells provide assistance primarily to B cells and cytotoxic T cells.
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The activation of T cells occurs predominantly in the thymus.
The activation of T cells occurs predominantly in the thymus.
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T cells can only recognize antigens presented by MHC class II molecules.
T cells can only recognize antigens presented by MHC class II molecules.
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CD8+ T cells directly kill infected cells as part of their effector function.
CD8+ T cells directly kill infected cells as part of their effector function.
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Memory T cells have a long lifespan and are important for rapid response upon re-exposure to antigens.
Memory T cells have a long lifespan and are important for rapid response upon re-exposure to antigens.
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Regulatory T cells help stimulate T cell responses by releasing IL-4.
Regulatory T cells help stimulate T cell responses by releasing IL-4.
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Autoimmunity results when self-reactive T cells are activated against self-antigens.
Autoimmunity results when self-reactive T cells are activated against self-antigens.
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The life cycle of a T cell includes clonal expansion after activation.
The life cycle of a T cell includes clonal expansion after activation.
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Severe Combined Immunodeficiency (SCID) typically results in low or absent T and B cells.
Severe Combined Immunodeficiency (SCID) typically results in low or absent T and B cells.
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Children with SCID have a great chance of survival past their second year without treatment.
Children with SCID have a great chance of survival past their second year without treatment.
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Immature T cells undergo clonal expansion before they are activated.
Immature T cells undergo clonal expansion before they are activated.
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The thymus is essential during the positive selection phase of T cell development.
The thymus is essential during the positive selection phase of T cell development.
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T cell effector functions can be performed in any peripheral tissue after differentiation.
T cell effector functions can be performed in any peripheral tissue after differentiation.
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Learning difficulties are a common feature of congenital heart problems.
Learning difficulties are a common feature of congenital heart problems.
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TCR rearrangement does not occur in immature T cells.
TCR rearrangement does not occur in immature T cells.
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B cell activation solely depends on interactions with CD8+ T cells.
B cell activation solely depends on interactions with CD8+ T cells.
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Peripheral tolerance is the same as central tolerance, occurring exclusively in the thymus.
Peripheral tolerance is the same as central tolerance, occurring exclusively in the thymus.
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Study Notes
Adaptive Immunity - T Cells
- T cells are part of the adaptive immune system, and are antigen-specific.
- T cells have two main functions:
- Helper T cells (Th) assist other immune responses.
- Cytotoxic T cells (CTL) kill cells infected by intracellular pathogens (and cancerous cells).
- T-cells originate in the bone marrow.
- T cells develop in the thymus.
- Immature T cells migrate from bone marrow to thymus.
- They undergo development in the thymus.
- Mature T cells leave the thymus. They are now naïve T cells and can be either CD4+ or CD8+.
- Naïve T cells are those which have not yet encountered an antigen.
- T-cell development involves receptor rearrangement.
- T-cell receptors (TCR) have a unique variable region (V) and a constant region (C).
- T-cell receptors have a unique antigen-binding site.
- Gene rearrangements generate specificities. The variable (V), diversity (D) and joining (J) regions from the gene segments are recombined randomly to create a large variety of TCRs.
- T-cells have checkpoints to ensure proper selection.
- These check if they have a TCR (T-cell receptor).
- They check if they can recognize an MHC (major histocompatibility complex) protein (positive selection).
- They check if they do not recognize self-antigens (negative selection).
- 98% of immature T cells do not leave the thymus; they die.
- T-cell activation occurs in lymph nodes.
- Mature/naïve T cells circulate through the secondary lymphoid organs (lymph nodes), where they await an encounter with an antigen.
- Activation of T cells requires 3 signals:
- Signal 1: TCR recognizes antigen presented on MHC molecule
- Signal 2: Co-stimulation (e.g., B7 on APC binds to CD28 on T cell)
- Signal 3: Instructive cytokines (e.g., IL-2, IL-12) that influence T cell differentiation.
- T cells produce different cytokines (proteins) which direct particular immune responses.
- T cells proliferate (clonal expansion) and differentiate into effector T cells and memory T cells.
- Effector T cells carry out their functions by interacting with other cells.
- Memory T cells are long-lived and provide immunological memory against that antigen.
- Effector T cells leave the lymph nodes to carry out their functions in the periphery.
T Cell Subsets
-
Helper T cells (CD4+):
- Th1: fights intracellular pathogens.
- Th2: fights helminth infections.
- Th17: fights extracellular pathogens.
- T Reg (regulatory): controls the immune response.
-
Cytotoxic T cells (CD8+): destroy infected or altered cells.
-
Cytokines direct different CD4+ T cell subsets to promote the appropriate immune response to various types of infections.
T Cell Immune Disorders
- DiGeorge syndrome is a deletion on chromosome 22, which means that the T-cell development pathway is abnormal.
- Severe Combined Immunodeficiency (SCID). Defects in different genes affecting T and B cells can lead to SCID which is fatal in early life. This can have serious consequences for the immune response because T/B cells cannot fight infections.
- Autoimmune disorders occur due to failures in tolerance mechanisms which prevent autoreactive T-cells from reacting to self-antigens. T-cells recognize and respond to self-antigens which leads to diseases (multiple sclerosis, rheumatoid arthritis, IBD).
T Cell Homeostasis
- When the antigen is cleared, most effector T cells die by apoptosis.
- T cells are deprived of signals such as antigen, CD28, and IL-2.
- Inhibitory pathways like CTLA-4 and PD-1 inhibit T cell activation.
- T regulatory cells help control the immune response and stop unnecessary T-cell response.
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Description
Explore the functions and development of T cells in the adaptive immune system. This quiz covers their role as Helper T cells and Cytotoxic T cells, along with their origin and maturation process in the thymus. Test your knowledge about T-cell receptors and their antigen specificity.
