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T helper cells are primarily involved in the innate immune system by directly engulfing pathogens.
Answer: False
Explanation: T helper cells are key components of the adaptive immune system, not the innate immune system, and their primary role is not direct phagocytosis.
T helper cells aid other immune cells by releasing signaling proteins called cytokines.
Answer: True
Explanation: Cytokines released by T helper cells act as signaling molecules that modulate the activity of various immune cells, including B cells, cytotoxic T cells, and phagocytes.
T helper cells facilitate antibody class switching in B cells solely by direct cell-to-cell contact without cytokine release.
Answer: False
Explanation: While cell-to-cell contact is involved, T helper cells primarily facilitate antibody class switching in B cells through the release of specific cytokines that signal B cells to differentiate.
T helper cells enhance phagocyte bactericidal activity by releasing cytokines that boost their killing mechanisms.
Answer: True
Explanation: Cytokines secreted by T helper cells, such as IFN-γ, activate macrophages and other phagocytes, enhancing their ability to kill ingested pathogens.
T helper cells can polarize the immune response to effectively combat different types of threats by releasing specific sets of cytokines.
Answer: True
Explanation: By secreting distinct cytokine profiles, T helper cells direct the immune system to mount appropriate responses against diverse pathogens, such as viruses, bacteria, or parasites.
Cytokines released by T helper cells are large structural proteins that form the physical barrier of the cell membrane.
Answer: False
Explanation: Cytokines are small signaling proteins that mediate communication between cells; they are not structural components of the cell membrane.
What is the primary role of T helper cells in the adaptive immune system?
Answer: Aiding other immune cells by releasing cytokines.
Explanation: T helper cells are crucial for coordinating the adaptive immune response by releasing cytokines that activate and direct other immune cells.
How do T helper cells contribute to antibody class switching in B cells?
Answer: By releasing cytokines that signal B cells to differentiate.
Explanation: T helper cells release cytokines that induce B cells to undergo antibody class switching, tailoring the antibody response to the specific pathogen.
What is the significance of the CD4 surface protein expressed by mature T helper cells?
Answer: It acts as a co-receptor for Class II MHC molecules, stabilizing T cell interaction.
Explanation: CD4 serves as a co-receptor that binds to Class II MHC molecules, stabilizing the interaction between the T cell receptor and the antigen-presenting cell.
How do T helper cells enhance the bactericidal activity of phagocytes like macrophages?
Answer: By releasing cytokines that boost the phagocytes' killing mechanisms.
Explanation: T helper cells release cytokines, such as IFN-γ, that activate macrophages and enhance their bactericidal capabilities.
What is the function of T helper cells in polarizing the immune response?
Answer: They release specific cytokine sets to tailor the response to different threats.
Explanation: T helper cells direct the immune response by releasing specific cytokine profiles that are appropriate for the type of pathogen encountered.
What is the primary function of cytokines released by T helper cells?
Answer: To signal and alter the behavior of target cells.
Explanation: Cytokines released by T helper cells act as signaling molecules that modify the behavior and function of target immune cells.
The CD4 surface protein on mature T helper cells binds to Class I Major Histocompatibility Complex (MHC) molecules.
Answer: False
Explanation: The CD4 co-receptor on T helper cells binds to Class II MHC molecules, not Class I MHC molecules.
CD4 acts as a co-receptor that stabilizes the interaction between the T cell receptor and Class II MHC molecules.
Answer: True
Explanation: CD4's binding to Class II MHC molecules stabilizes the T cell receptor's interaction with the peptide-MHC complex, facilitating T cell activation.
The primary professional antigen-presenting cells that interact with CD4+ T cells include T cytotoxic cells and NK cells.
Answer: False
Explanation: Primary professional APCs interacting with CD4+ T cells are dendritic cells, macrophages, and B cells. Cytotoxic T cells and NK cells have different primary roles.
T helper cell activation requires TCR binding to peptide-MHC complexes and co-receptor binding to MHC, but not cell-to-cell interactions like CD40/CD40L.
Answer: False
Explanation: Effective T helper cell activation requires TCR-MHC binding, CD4 co-receptor binding, and crucial co-stimulatory signals, such as CD40-CD40L interactions.
Signal 1 in T cell activation involves the release of cytokines from the APC to the T cell.
Answer: False
Explanation: Signal 1 primarily involves the recognition of the antigen-MHC complex by the TCR and CD4 co-receptor, not cytokine release.
Lck kinase is recruited by CD4 binding to MHC molecules and phosphorylates ITAMs on CD3 chains to initiate T cell signaling.
Answer: True
Explanation: CD4 binding to MHC recruits Lck kinase, which then phosphorylates ITAMs on the CD3 chains, initiating the TCR signaling cascade.
CD45 inhibits Lck activity by phosphorylating its C-terminal tail.
Answer: False
Explanation: CD45 dephosphorylates Lck, thereby activating it, while Csk phosphorylates Lck to inhibit its activity.
Signal 2, the survival signal, involves the interaction of CD28 on T cells with CD80/CD86 on APCs and is crucial for preventing T cell anergy.
Answer: True
Explanation: Signal 2, mediated by CD28-CD80/CD86 interactions, provides essential co-stimulation to prevent T cell anergy and ensure proper activation.
A naive T cell receiving Signal 1 but not Signal 2 will become hyperactive and aggressively attack all antigens.
Answer: False
Explanation: Receiving Signal 1 without Signal 2 typically leads to anergy (unresponsiveness), not hyperactivity.
Signal 3 in T cell activation primarily involves the release of chemokines to recruit other immune cells.
Answer: False
Explanation: Signal 3 is primarily associated with cytokine-mediated differentiation and proliferation, such as IL-2 driving clonal expansion.
CD154 (CD40L) on activated T cells interacts with CD40 on other cells, serving as a key mediator of T cell helper function.
Answer: True
Explanation: CD154 (CD40L) is critical for T cell helper function, mediating interactions with CD40 on target cells to promote immune responses.
The TCR-CD3 complex is solely responsible for antigen recognition, with CD4 playing no role in initiating T cell activation signaling.
Answer: False
Explanation: While the TCR recognizes the antigen, CD4 plays a critical role in stabilizing the interaction and recruiting Lck kinase, which is essential for initiating signaling.
CD4's interaction with MHC class II molecules primarily serves to block Lck kinase recruitment to the TCR complex.
Answer: False
Explanation: CD4's interaction with MHC class II molecules stabilizes the TCR-MHC binding and facilitates Lck kinase recruitment, thereby promoting T cell activation.
APCs present antigens on MHC Class I molecules to initiate T helper cell responses.
Answer: False
Explanation: APCs present antigens on MHC Class II molecules to initiate T helper cell responses, while MHC Class I presents antigens to cytotoxic T cells.
MHC Class I molecules typically present peptides that are 12-25 amino acids long, while MHC Class II molecules present shorter peptides of 9-10 amino acids.
Answer: False
Explanation: MHC Class I molecules typically present peptides of 9-10 amino acids, while MHC Class II molecules present longer peptides, generally 12-25 amino acids.
CD45RO, found on activated cells, is thought to facilitate easier interactions as an effector cell.
Answer: True
Explanation: The CD45RO isoform, expressed on activated and memory T cells, is proposed to facilitate more efficient signaling compared to the CD45RA isoform on naive cells.
ZAP-70 is a phosphatase that deactivates the TCR complex after Lck phosphorylation.
Answer: False
Explanation: ZAP-70 is a kinase that binds to phosphorylated ITAMs and initiates downstream signaling, rather than deactivating the TCR complex.
Which of the following is NOT a primary professional antigen-presenting cell (APC) that interacts with CD4+ T cells?
Answer: Cytotoxic T cells
Explanation: Dendritic cells, macrophages, and B cells are the primary professional APCs that present antigens on MHC Class II molecules to CD4+ T cells.
Which of the following is crucial for effective T helper cell activation during interaction with APCs?
Answer: CD40-CD40L interaction and cytokine release
Explanation: Effective T helper cell activation requires not only TCR-MHC binding and CD4 co-receptor interaction but also co-stimulatory signals like CD40-CD40L and cytokine signaling.
What is Signal 1 in the three-signal model for T cell activation?
Answer: Recognition of antigen-MHC complex by TCR and CD4 co-receptor
Explanation: Signal 1 represents the initial recognition of the antigen-MHC complex by the T cell receptor (TCR) and its co-receptor (CD4 or CD8).
What is the role of Lck kinase in T cell activation?
Answer: It is recruited by CD4 binding to MHC and phosphorylates ITAMs on CD3 chains.
Explanation: Lck kinase is recruited to the TCR complex via CD4 binding to MHC and phosphorylates ITAMs, initiating the downstream signaling cascade.
How does CD45 regulate Lck activity during T cell activation?
Answer: By dephosphorylating Lck, thereby activating it.
Explanation: CD45 acts as a phosphatase, dephosphorylating Lck and promoting its kinase activity, which is essential for initiating T cell signaling.
What is the importance of Signal 2 in T cell activation?
Answer: It prevents T cell anergy and ensures response to foreign antigens.
Explanation: Signal 2, provided by co-stimulatory molecules, is critical for preventing T cell anergy and ensuring that the T cell responds appropriately to foreign antigens.
What is the typical outcome if a naive T cell receives Signal 1 (antigen recognition) but not Signal 2 (co-stimulation)?
Answer: The cell enters a state of anergy (unresponsiveness).
Explanation: Without Signal 2, a naive T cell that receives Signal 1 typically becomes anergic, meaning it becomes unresponsive to subsequent antigen stimulation.
What is Signal 3 in T cell activation primarily associated with?
Answer: Proliferation and clonal expansion via IL-2
Explanation: Signal 3 involves the release of IL-2, which acts in an autocrine manner to drive the proliferation and clonal expansion of activated T helper cells.
What is the role of CD154 in T helper cell function?
Answer: It interacts with CD40 on other cells to mediate crucial signaling for immune responses.
Explanation: CD154 (CD40L) on T helper cells binds to CD40 on other cells, mediating essential co-stimulatory signals for effective immune responses.
What is the role of the TCR-CD3 complex in T helper cell activation?
Answer: It initiates intracellular signaling pathways upon antigen recognition.
Explanation: The TCR-CD3 complex is responsible for recognizing the antigen-MHC complex and initiating the intracellular signaling cascade required for T cell activation.
How does CD4 influence the interaction between T helper cells and MHC molecules?
Answer: It stabilizes the TCR-MHC binding and recruits Lck kinase.
Explanation: CD4 stabilizes the TCR-MHC interaction and recruits Lck kinase, both critical steps for initiating T cell activation signaling.
What is the role of APCs in initiating T helper cell responses?
Answer: They capture, process, and present antigens on MHC Class II molecules.
Explanation: APCs initiate T helper cell responses by capturing, processing, and presenting antigens on MHC Class II molecules to naive T helper cells.
What is the typical difference in peptide length presented by MHC Class I versus MHC Class II molecules?
Answer: MHC Class II presents longer peptides (12-25 aa) than MHC Class I (9-10 aa).
Explanation: MHC Class I typically presents peptides of 9-10 amino acids, while MHC Class II molecules present longer peptides, generally 12-25 amino acids.
How do CD45 isoforms relate to T helper cell activation and function?
Answer: CD45 shortens after activation (RA to RO), with RO potentially facilitating easier interactions.
Explanation: CD45 isoforms change upon activation; the shorter CD45RO isoform, found on activated cells, may facilitate more efficient signaling.
What is the role of ZAP-70 in T cell signaling?
Answer: It binds to phosphorylated ITAMs via its SH2 domain and orchestrates downstream signaling.
Explanation: ZAP-70 binds to phosphorylated ITAMs on the CD3 chains and initiates the downstream signaling cascade necessary for T cell activation.
Th0 cells are the final differentiated effector cells and do not further differentiate into specialized subtypes.
Answer: False
Explanation: Th0 cells are precursor cells that differentiate into specialized subtypes like Th1 or Th2 based on the cytokine environment.
The differentiation of Th2 cells is primarily governed by the transcription factors STAT4 and T-bet.
Answer: False
Explanation: Th2 cell differentiation is primarily governed by STAT6 and GATA3, while STAT4 and T-bet are associated with Th1 differentiation.
Th1 and Th2 cells exhibit cooperative regulation, where IFN-γ enhances Th2 development and IL-4 enhances Th1 development.
Answer: False
Explanation: Th1 and Th2 cells exhibit reciprocal inhibition; IFN-γ from Th1 inhibits Th2 development, and IL-4 from Th2 inhibits Th1 development.
The traditional Th1/Th2 model is considered a complete and accurate representation of all T helper cell functions and differentiation pathways.
Answer: False
Explanation: The Th1/Th2 model is an oversimplification, as other subsets (like Th17) exist, and cell plasticity suggests a more complex differentiation landscape.
What are Th0 cells, and how do they differentiate?
Answer: They are the initial stage of activated T helper cells that differentiate into Th1 or Th2 based on cytokine environment.
Explanation: Th0 cells are the precursor T helper cells that differentiate into specialized subtypes like Th1 or Th2, guided by the cytokine milieu.
Which transcription factors are primarily associated with Th1 cell differentiation?
Answer: STAT4 and T-bet
Explanation: The differentiation of Th1 cells is primarily regulated by the transcription factors STAT4 and T-bet.
How do Th1 and Th2 cells typically influence each other's development?
Answer: They exhibit reciprocal inhibition, where Th1 cytokines inhibit Th2 and vice versa.
Explanation: Th1 and Th2 cells engage in reciprocal inhibition; Th1 cytokines suppress Th2 development, and Th2 cytokines suppress Th1 development.
What is a limitation of the traditional Th1/Th2 model of T helper cell differentiation?
Answer: It oversimplifies T helper cell function, as seen with IL-10's role in humans and cell plasticity.
Explanation: The traditional Th1/Th2 model is an oversimplification, failing to encompass the complexity of other subsets and the plasticity observed in T helper cell differentiation.
Th1 cells primarily promote humoral immunity and are involved in responses against extracellular parasites.
Answer: False
Explanation: Th1 cells primarily promote cell-mediated immunity and target intracellular pathogens, while Th2 cells are involved in humoral immunity and extracellular parasites.
Tₕ1 cells are primarily effective against intracellular bacteria and protozoa, aiding in the clearance of infections where pathogens reside within host cells.
Answer: True
Explanation: Tₕ1 helper cells are crucial for cell-mediated immunity and are particularly effective against intracellular bacteria and protozoa.
Tₕ2 cells are primarily responsible for driving humoral immunity and are particularly effective against extracellular parasites.
Answer: True
Explanation: Tₕ2 helper cells orchestrate humoral immunity, focusing on B cell activation and antibody production, and are key in combating extracellular parasites.
Th17 cells produce IL-4 and IL-5, and are primarily involved in responses against intracellular pathogens.
Answer: False
Explanation: Th17 cells produce IL-17, IL-21, and IL-22, and are primarily involved in defense against extracellular pathogens and fungi, particularly at mucosal surfaces.
Th17 cells primarily defend against intracellular bacteria and protozoa by producing IFN-γ and IL-2.
Answer: False
Explanation: Th17 cells primarily defend against extracellular pathogens and fungi by producing IL-17, IL-21, and IL-22, not IFN-γ and IL-2.
Th9 cells produce IL-17 and are primarily involved in defense against extracellular bacteria.
Answer: False
Explanation: Th9 cells produce IL-9 and are involved in defense against helminth infections, not IL-17 and extracellular bacteria.
What type of immune response is mediated by Th1 cells, and what pathogens do they primarily target?
Answer: Cell-mediated immunity; intracellular bacteria and protozoa
Explanation: Th1 cells drive cell-mediated immunity and are crucial for combating intracellular pathogens like bacteria and protozoa.
What are the key effector cytokines produced by Th1 cells?
Answer: IFN-γ and IL-2
Explanation: The primary effector cytokines produced by Th1 cells are interferon-gamma (IFN-γ) and interleukin-2 (IL-2).
What type of immune response is mediated by Th2 cells, and what pathogens do they primarily target?
Answer: Humoral immunity; extracellular parasites
Explanation: Th2 cells mediate humoral immunity, primarily targeting extracellular parasites and contributing to allergic responses.
Which cytokine produced by Th2 cells is critical for stimulating B cells to produce IgE antibodies?
Answer: IL-4
Explanation: IL-4, produced by Th2 cells, is essential for inducing B cells to switch to producing IgE antibodies and also promotes Th2 differentiation.
What is the primary role of Th17 cells in the immune system?
Answer: Defending against extracellular pathogens and fungi, especially at mucosal surfaces.
Explanation: Th17 cells are crucial for immunity against extracellular pathogens and fungi, particularly at mucosal sites, due to their production of IL-17 and other pro-inflammatory cytokines.
What is the key effector cytokine produced by THαβ helper cells, and what is their role?
Answer: IL-10; activating NK cells and CD8 T cells against viruses
Explanation: THαβ helper cells produce IL-10 and are involved in host immunity against viruses by activating NK cells and CD8 T cells.
What are the primary functions of Th17 cells in immunity?
Answer: Defending against extracellular pathogens and fungi, particularly at mucosal surfaces.
Explanation: Th17 cells are crucial for defense against extracellular pathogens and fungi, especially at mucosal surfaces, due to their production of IL-17 and related cytokines.
What is the role of Th9 cells in the immune system?
Answer: They produce IL-9 and are involved in defending against helminth infections.
Explanation: Th9 cells produce IL-9 and are implicated in the immune response against helminth infections.
Genetic variations in CD4+ cells are linked to an increased susceptibility to autoimmune diseases.
Answer: True
Explanation: Genetic variations affecting CD4+ cell function can indeed predispose individuals to various autoimmune diseases.
The provided text explicitly details the specific mechanisms by which T helper cells contribute to antitumor immunity.
Answer: False
Explanation: The text generally indicates a role for T helper cells in coordinating immune responses, suggesting a potential contribution to antitumor immunity, but does not detail specific mechanisms.
T helper cells are not involved in hypersensitivity reactions, which are solely mediated by B cells and antibodies.
Answer: False
Explanation: T helper cells, particularly Th2 cells, play a significant role in Type 1 hypersensitivity (allergic reactions), and Th1 cells in Type 4 hypersensitivity.
Type 1 hypersensitivity reactions, like asthma, are primarily mediated by Th1 cells promoting IgG antibody production.
Answer: False
Explanation: Type 1 hypersensitivity reactions are primarily mediated by Th2 cells, which promote IgE antibody production, leading to mast cell degranulation.
Type 4 hypersensitivity is primarily mediated by Th2 cells and involves rapid antibody-mediated inflammation.
Answer: False
Explanation: Type 4 hypersensitivity is primarily mediated by Th1 cells and activated macrophages, leading to delayed inflammation, not rapid antibody-mediated inflammation.
T helper cells, particularly Th2 cells, are implicated in autoimmune diseases like lupus due to their cytokine production.
Answer: True
Explanation: Evidence suggests that Th2 cells and their associated cytokines may contribute to the pathogenesis of autoimmune diseases such as lupus.
CD4+ T cells are not essential for the development of cytotoxic T cell-mediated autoimmunity or transplant rejection, as these are primarily CD8+ T cell functions.
Answer: False
Explanation: CD4+ T cells are essential for providing IL-2, which supports the proliferation and activation of cytotoxic T cells involved in autoimmunity and transplant rejection.
HIV primarily targets and infects CD8+ T cells, leading to a depletion of cytotoxic T cells.
Answer: False
Explanation: HIV primarily targets and infects CD4+ T cells, leading to their depletion and subsequent immune deficiency.
Pyroptosis is a non-inflammatory cell death that protects CD4+ T cells during HIV infection.
Answer: False
Explanation: Pyroptosis is a highly inflammatory form of cell death that contributes to CD4+ T cell depletion during HIV infection.
Severe depletion of CD4+ T cells in AIDS patients leads to enhanced stimulation of CD8+ T cells and improved antibody production.
Answer: False
Explanation: Severe CD4+ T cell depletion in AIDS patients compromises immune function, leading to impaired CD8+ T cell stimulation and reduced antibody production.
COVID-19 is associated with an increase in CD4+ T cell counts, which correlates with better patient outcomes.
Answer: False
Explanation: COVID-19 is associated with a decline in CD4+ T cell counts, and lower counts correlate with poorer patient outcomes, such as ICU admission.
Understanding T helper cell responses is not crucial for improving the effectiveness of vaccination strategies.
Answer: False
Explanation: Understanding T helper cell responses is crucial for developing more potent and effective vaccination strategies.
Interleukin-2 (IL-2), released by activated T helper cells, acts in a paracrine manner to stimulate B cell proliferation.
Answer: False
Explanation: IL-2 released by activated T helper cells primarily acts in an autocrine manner to stimulate T cell proliferation and clonal expansion.
Regulatory T cells and Th3 cells, unlike effector T helper cells, function to amplify immune responses against pathogens.
Answer: False
Explanation: Regulatory T cells and Th3 cells modulate and suppress immune responses to maintain tolerance, whereas effector T helper cells amplify responses against pathogens.
A high CD4+/CD8+ ratio signifies immune deficiency and progression towards AIDS.
Answer: False
Explanation: A low CD4+/CD8+ ratio, resulting from CD4+ T cell depletion, signifies immune deficiency and progression towards AIDS.
Genetic variations in CD4+ cells are linked to an increased susceptibility to which type of disease?
Answer: Autoimmune diseases
Explanation: Genetic variations affecting CD4+ cell function are associated with an increased risk of developing autoimmune diseases.
According to the provided text, what is the role of T helper cells in antitumor immunity?
Answer: The text generally suggests a role in coordinating immune cells, implying a potential role in eliminating tumor cells.
Explanation: While not detailed, the text implies T helper cells' role in coordinating immune responses suggests a potential involvement in antitumor immunity.
How can T helper cells be involved in hypersensitivity reactions?
Answer: Th2 cells can contribute to Type 1 (allergic) hypersensitivity, and Th1 cells to Type 4 (delayed-type) hypersensitivity.
Explanation: Th2 cells are implicated in Type 1 hypersensitivity (allergies), while Th1 cells contribute to Type 4 (delayed-type) hypersensitivity.
What is the role of T helper cells in Type 1 hypersensitivity reactions like asthma?
Answer: Th2 cells promote IgE production.
Explanation: Th2 cells promote the production of IgE antibodies, which are central to the mechanism of Type 1 hypersensitivity reactions like asthma.
What is the connection between T helper cells and Type 4 (delayed-type) hypersensitivity?
Answer: Th1 cells activate macrophages, leading to chronic inflammation.
Explanation: Th1 cells activate macrophages, which contribute to the chronic inflammation characteristic of Type 4 (delayed-type) hypersensitivity.
Which T helper cell subset is suggested by the text to play a role in autoimmune diseases like lupus?
Answer: Th2 cells
Explanation: The text suggests that Th2 cells may be implicated in the pathogenesis of autoimmune diseases such as lupus.
How do CD4+ T cells contribute to cytotoxic T cell-mediated autoimmunity and transplant rejection?
Answer: By providing IL-2 to support the proliferation and activation of auto-reactive or alloreactive killer T cells.
Explanation: CD4+ T cells provide essential IL-2, which fuels the proliferation and activation of cytotoxic T cells involved in autoimmune responses and transplant rejection.
What is the primary impact of HIV infection on CD4+ T cells?
Answer: HIV infects and depletes CD4+ T cells, leading to immune deficiency.
Explanation: HIV primarily infects CD4+ T cells, causing their progressive depletion, which results in severe immune deficiency characteristic of AIDS.
What is pyroptosis and its link to HIV infection?
Answer: A highly inflammatory cell death triggered by abortively infected CD4+ T cells, contributing to depletion.
Explanation: Pyroptosis is an inflammatory cell death pathway triggered by abortively infected CD4+ T cells in HIV, contributing to cell depletion and chronic inflammation.
What are the consequences of severe CD4+ T cell depletion in AIDS patients?
Answer: Increased susceptibility to opportunistic infections and cancers due to compromised immunity.
Explanation: Severe CD4+ T cell depletion in AIDS patients leads to profound immune compromise, increasing vulnerability to opportunistic infections and cancers.
How does COVID-19 affect CD4+ T cells?
Answer: COVID-19 is associated with a decline in CD4+ T cells, correlating with ICU admission.
Explanation: COVID-19 patients often exhibit a decline in CD4+ T cell counts, which is correlated with disease severity and ICU admission.
What is the significance of understanding T helper cell responses in the context of vaccination?
Answer: It helps in developing more potent vaccines that elicit stronger immunity.
Explanation: Understanding T helper cell functions is vital for designing vaccines that induce robust and protective immune responses.
What is the function of Interleukin-2 (IL-2) in T helper cells?
Answer: It acts in an autocrine manner to stimulate T cell proliferation and clonal expansion.
Explanation: IL-2 is a growth factor released by activated T helper cells that acts autocrinely to promote their proliferation and clonal expansion.
How do regulatory T cells and Th3 cells differ from effector T helper cells?
Answer: Regulatory T cells and Th3 cells modulate and suppress immune responses, while effector cells promote them.
Explanation: Regulatory T cells and Th3 cells function to suppress and modulate immune responses, contrasting with effector T helper cells that promote and amplify immune responses.
What does the CD4+/CD8+ ratio indicate regarding immune health?
Answer: It is an indicator of immune system health, with a decline signifying immune deficiency.
Explanation: The CD4+/CD8+ ratio serves as a marker of immune system health; a declining ratio typically indicates immune deficiency, as seen in conditions like HIV/AIDS.
Memory T cells are short-lived cells that are generated after an initial encounter with an antigen and provide no long-term immunity.
Answer: False
Explanation: Memory T cells are long-lived and provide immunological memory, enabling a faster and more robust response upon re-exposure to an antigen.
Memory T cells are primed to respond more rapidly and efficiently than naive T cells.
Answer: True
Explanation: A key characteristic of memory T cells is their enhanced responsiveness, allowing for quicker and stronger immune reactions upon secondary antigen exposure.
What is the significance of memory T cells in the immune system?
Answer: They provide immunological memory for a faster and more robust response upon re-exposure.
Explanation: Memory T cells are crucial for establishing immunological memory, enabling a rapid and potent secondary immune response upon re-encountering a specific antigen.
How do memory T cells differ from naive T cells in terms of activation?
Answer: Memory T cells are primed to respond more rapidly and efficiently than naive T cells.
Explanation: Memory T cells are pre-activated and can mount a faster and more potent response compared to naive T cells upon antigen re-exposure.