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Questions and Answers
What is the primary function of TLR-3 in immune response?
What is the primary function of TLR-3 in immune response?
Which of the following describes the role of the complement system in tackling extracellular pathogens?
Which of the following describes the role of the complement system in tackling extracellular pathogens?
What is the limited role of the complement system after intracellular bacteria have entered host cells?
What is the limited role of the complement system after intracellular bacteria have entered host cells?
Which of the following best describes opsonization in the context of the complement system?
Which of the following best describes opsonization in the context of the complement system?
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What type of molecules does TLR-3 specifically recognize?
What type of molecules does TLR-3 specifically recognize?
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What is the primary role of Helper T Cells in the immune response?
What is the primary role of Helper T Cells in the immune response?
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What mechanism do Cytotoxic T Cells use to eliminate infected or cancerous cells?
What mechanism do Cytotoxic T Cells use to eliminate infected or cancerous cells?
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Which subtype of Helper T Cells is primarily involved in responses against extracellular parasites?
Which subtype of Helper T Cells is primarily involved in responses against extracellular parasites?
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What is the main function of Memory T Cells?
What is the main function of Memory T Cells?
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Which of the following best describes the primary function of B Cells in the immune response?
Which of the following best describes the primary function of B Cells in the immune response?
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Study Notes
Endosomal TLR-3
- TLR-3 is an endosomal pattern recognition receptor present in immune cells.
- It specifically recognizes double-stranded RNA (dsRNA), commonly associated with RNA viral infections.
- Activation of TLR-3 leads to an antiviral immune response when dsRNA is detected during viral replication.
Complement System Overview
- Comprises a group of proteins in blood that enhance antibody and phagocytic immune responses.
- Main functions include opsonization (coating pathogens for phagocytosis), lysis (forming membrane attack complex to kill pathogens), and promoting inflammation via anaphylatoxins (C3a, C5a).
Complement's Role with Intracellular Bacteria
- Opsonization helps prepare extracellular bacteria for phagocytosis before host cell entry.
- Once bacteria enter host cells, the complement system's direct impact is limited, as it cannot access these intracellular spaces.
T Cells (T Lymphocytes)
- Key players in adaptive immunity, maturing in the thymus gland and eliminating infected/cancerous cells.
- Types include Helper T Cells (CD4+), Cytotoxic T Cells (CD8+), and Memory T Cells.
Helper T Cells (CD4+ T Cells)
- Secrete cytokines to assist other immune responses.
- Activate B cells for antibodies, stimulate cytotoxic T cells, and coordinate immune activity.
- Subtypes include:
- Th1: Targets intracellular pathogens like viruses.
- Th2: Aids in responses to extracellular parasites and allergens.
- Th17: Involved in fungi response and autoimmune diseases.
- Regulatory T Cells (Tregs): Suppress immune responses to prevent autoimmunity.
Cytotoxic T Cells (CD8+ T Cells)
- Function to directly kill infected or malignant cells.
- Identify infected cells through MHC I antigen presentation and induce apoptosis via perforin and granzymes.
Memory T Cells
- Provide long-term immunity and a quicker response upon re-exposure to antigens.
B Cells (B Lymphocytes)
- Mature in bone marrow, primarily responsible for antibody production.
- Functions include:
- Producing specific antibodies that neutralize pathogens or mark them for destruction.
- Presenting antigens on MHC II to helper T cells, enhancing the immune response.
Mechanisms of Antigen Presentation
- MHC Class II molecules present exogenous antigens to CD4+ T cells after processing by antigen-presenting cells (APCs).
- MHC I molecules present intracellular antigens, crucial for activating CD8+ T cells.
Cross-Presentation
- Allows dendritic cells to present extracellular antigens on MHC I, crucial for activating CD8+ T cells against non-directly infected cells.
- Mechanisms include:
- Cytosolic Pathway: Antigens processed in the cytosol, then loaded onto MHC I.
- Vacuolar Pathway: Antigens processed within endosomes, with direct loading onto MHC I.
Clinical Relevance of Cross-Presentation
- Important for vaccine development and cancer immunotherapies targeting CD8+ T cells.
- Mismanaged cross-presentation may lead to autoimmune diseases.
Cytoplasmic and Endosomal DAMPs
- DAMPs signify stress or damage in cells, recognized by the immune system.
- Primarily related to tissue damage rather than direct viral recognition.
Extracellular TLR-2
- TLR-2 is located on innate immune cell surfaces, recognizing bacterial components and some viral proteins.
- Primarily associated with bacterial infections rather than viral.
Cytoplasmic NOD-like Receptors (NLRs)
- Recognize bacterial components in the cytoplasm, activating inflammatory responses.
- Less involved in viral recognition compared to bacterial infections.
Complement System and Intracellular Bacteria
- Operates mainly against extracellular pathogens; limited effectiveness against intracellular bacteria.
- Cell-mediated immunity, especially CD8+ T cells and macrophages, is crucial for managing intracellular infections.
Summary of Immune Response
- The complement system aids in the initial response but relies more on cell-mediated immunity after pathogens enter cells.
- B cells, through humoral immunity, actively produce antibodies to neutralize extracellular pathogens and toxins.
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Description
Explore the crucial role of TLR-3 in immune response as a pattern recognition receptor located in endosomes. This quiz covers the function of TLR-3 in recognizing double-stranded RNA (dsRNA) during viral infections, emphasizing its importance in the immune defense mechanism. Test your knowledge on this vital component of the immune system!
