Podcast
Questions and Answers
What is a key characteristic of stem cells?
What is a key characteristic of stem cells?
- Self-renewal (correct)
- Specialized structure
- Inability to replicate
- Limited lifespan
Which property enables stem cells to differentiate into various cell types?
Which property enables stem cells to differentiate into various cell types?
- Self-renewal
- Immortality
- Potency (correct)
- Quiescence
Where are embryonic stem cells primarily isolated from?
Where are embryonic stem cells primarily isolated from?
- Bone marrow
- Adult skin tissue
- Umbilical cord blood
- Inner cell mass of blastocysts (correct)
Which of the following is a source of adult stem cells?
Which of the following is a source of adult stem cells?
What is a primary medical application of stem cells?
What is a primary medical application of stem cells?
What process is involved in cell-based therapies using stem cells?
What process is involved in cell-based therapies using stem cells?
Which of the following is treated using bone marrow transplantation, leveraging the properties of stem cells?
Which of the following is treated using bone marrow transplantation, leveraging the properties of stem cells?
What cells are targeted for replacement in the treatment of type 1 diabetes mellitus using stem cells?
What cells are targeted for replacement in the treatment of type 1 diabetes mellitus using stem cells?
Which cells are responsible for capturing and transporting antigens to the peripheral lymphoid tissues?
Which cells are responsible for capturing and transporting antigens to the peripheral lymphoid tissues?
Which of the following is NOT a primary function of antigen-presenting cells (APCs)?
Which of the following is NOT a primary function of antigen-presenting cells (APCs)?
Where are antigen-presenting cells (APCs) typically found?
Where are antigen-presenting cells (APCs) typically found?
Which molecule is richly expressed on antigen-presenting cells (APCs) and is crucial for antigen presentation?
Which molecule is richly expressed on antigen-presenting cells (APCs) and is crucial for antigen presentation?
What is the first step in the role of antigen-presenting cells?
What is the first step in the role of antigen-presenting cells?
What is the eventual outcome of extracellular antigen processing and presentation by APCs?
What is the eventual outcome of extracellular antigen processing and presentation by APCs?
Which process degrades cytosolic proteins in antigen processing?
Which process degrades cytosolic proteins in antigen processing?
To which cells are peptides from cytosolic antigens presented, and on which molecule?
To which cells are peptides from cytosolic antigens presented, and on which molecule?
Which cells are primarily responsible for phagocytosis?
Which cells are primarily responsible for phagocytosis?
What is the major difference between monocytes and macrophages?
What is the major difference between monocytes and macrophages?
Which type of leukocytes is most abundant in the blood?
Which type of leukocytes is most abundant in the blood?
What does an increased number of neutrophils in the blood typically indicate?
What does an increased number of neutrophils in the blood typically indicate?
What is the process by which phagocytes migrate through the blood vessel walls to enter tissues?
What is the process by which phagocytes migrate through the blood vessel walls to enter tissues?
Which factor is involved in attracting phagocytes towards microbes in tissues?
Which factor is involved in attracting phagocytes towards microbes in tissues?
What is the role of Opsonins in phagocytosis?
What is the role of Opsonins in phagocytosis?
What is the name of the structure formed when a phagocyte's cell membrane encloses a microbe?
What is the name of the structure formed when a phagocyte's cell membrane encloses a microbe?
What structure results from the fusion of a phagosome and a lysosome?
What structure results from the fusion of a phagosome and a lysosome?
Which of the following is an oxygen-dependent mechanism of intracellular killing by phagocytes?
Which of the following is an oxygen-dependent mechanism of intracellular killing by phagocytes?
How does lactoferrin contribute to intracellular killing?
How does lactoferrin contribute to intracellular killing?
What happens to neutrophils after phagocytosis?
What happens to neutrophils after phagocytosis?
Following digestion in macrophages, what happens to microbial antigens?
Following digestion in macrophages, what happens to microbial antigens?
Which of the following is NOT an oxygen-independent mechanism employed by phagocytes to kill intracellular pathogens:
Which of the following is NOT an oxygen-independent mechanism employed by phagocytes to kill intracellular pathogens:
A researcher is studying a novel treatment aimed at enhancing the intracellular killing of bacteria within macrophages. Which of the following strategies would MOST directly target an oxygen-dependent killing mechanism?
A researcher is studying a novel treatment aimed at enhancing the intracellular killing of bacteria within macrophages. Which of the following strategies would MOST directly target an oxygen-dependent killing mechanism?
In the context of antigen presentation, a mutation that disrupts the function of the proteasome would MOST directly impair which of the following processes?
In the context of antigen presentation, a mutation that disrupts the function of the proteasome would MOST directly impair which of the following processes?
A patient with a genetic defect is unable to produce functional Class II MHC molecules. This defect would MOST directly affect the ability of which cell type to activate T helper cells?
A patient with a genetic defect is unable to produce functional Class II MHC molecules. This defect would MOST directly affect the ability of which cell type to activate T helper cells?
A researcher discovers a novel bacterial strain that is resistant to phagocytosis. Further investigation reveals that the bacteria is producing an enzyme that cleaves C3b. What is the MOST likely mechanism by which this enzyme is promoting bacterial survival?
A researcher discovers a novel bacterial strain that is resistant to phagocytosis. Further investigation reveals that the bacteria is producing an enzyme that cleaves C3b. What is the MOST likely mechanism by which this enzyme is promoting bacterial survival?
What is a key distinction between the roles of CD4+ and CD8+ T cells in the adaptive immune response, specifically concerning antigen presentation pathways?
What is a key distinction between the roles of CD4+ and CD8+ T cells in the adaptive immune response, specifically concerning antigen presentation pathways?
An experiment introduces a chemical inhibitor that specifically blocks diapedesis. This inhibitor would MOST directly prevent which of the following?
An experiment introduces a chemical inhibitor that specifically blocks diapedesis. This inhibitor would MOST directly prevent which of the following?
A novel drug is designed to enhance the fusion of phagosomes with lysosomes in macrophages. What effect would administering this drug MOST likely have on intracellular pathogens
A novel drug is designed to enhance the fusion of phagosomes with lysosomes in macrophages. What effect would administering this drug MOST likely have on intracellular pathogens
A hypothetical virus named “Obliteratus” has evolved a sophisticated strategy to evade immune detection. After infecting a cell, it produces a protein that directly prevents the infected cell from expressing MHC class I molecules on its surface. How does this viral strategy MOST directly benefit the virus?
A hypothetical virus named “Obliteratus” has evolved a sophisticated strategy to evade immune detection. After infecting a cell, it produces a protein that directly prevents the infected cell from expressing MHC class I molecules on its surface. How does this viral strategy MOST directly benefit the virus?
Consider an extremely rare genetic disorder that results in phagocytes lacking the ability to produce myeloperoxidase, a crucial element in the generation of hypochlorous acid (a potent antimicrobial agent) within phagolysosomes. Which of the following would be the MOST direct consequence of this genetic defect on an individual's immune response?
Consider an extremely rare genetic disorder that results in phagocytes lacking the ability to produce myeloperoxidase, a crucial element in the generation of hypochlorous acid (a potent antimicrobial agent) within phagolysosomes. Which of the following would be the MOST direct consequence of this genetic defect on an individual's immune response?
Flashcards
Stem Cells
Stem Cells
Undifferentiated cells capable of self-renewal and differentiation into specialized cell types.
Self-renewal (stem cell)
Self-renewal (stem cell)
The ability of a stem cell to maintain itself in an undifferentiated state.
Stem Cell Potency
Stem Cell Potency
The capacity of a stem cell to differentiate into specialized cell types (e.g., muscle, nerve, blood).
Embryonic Stem Cells
Embryonic Stem Cells
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Adult Stem Cells
Adult Stem Cells
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Phagocytes
Phagocytes
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Monocytes
Monocytes
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Macrophages
Macrophages
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Neutrophils
Neutrophils
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Diapedesis
Diapedesis
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Chemotaxis
Chemotaxis
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Phagocyte Recognition
Phagocyte Recognition
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Opsonins
Opsonins
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Phagosome Formation
Phagosome Formation
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Phagolysosome
Phagolysosome
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Intracellular killing
Intracellular killing
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Lysosomal granules
Lysosomal granules
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Study Notes
- Stem cells are undifferentiated or unspecialized cells
Stem Cell Properties
- Self-renewal: Stem cells can maintain themselves in an undifferentiated state.
- Potency: Stem cells can differentiate into specialized cell types, like muscle, red blood, nerve, or brain cells.
Types of Mammalian Stem Cells
- Embryonic Stem Cells: Isolated from the inner cell mass of blastocysts.
- Adult Stem Cells: Found in adult tissues such as skin, muscles, umbilical cord blood, brain, heart, and bone marrow.
Medical Importance of Stem Cells
- Stem cell therapy can change the treatment of human diseases.
- Human stem cells are used to generate cells and tissues for cell-based therapies.
- Cell-based therapies involve treating patients by transplanting specialized cells grown from stem cells in the laboratory (stem cell culture).
Uses of Stem Cells
- Leukemia treatment involves bone marrow transplants to replace abnormal stem cells with those that produce healthy blood cells.
- Cardiovascular disease treatment: Repairing damaged heart cells after a heart attack.
- Type 1 Diabetes Mellitus treatment: Replacing damaged pancreatic beta cells, enabling insulin secretion.
- Spinal cord injuries treatment: Regrowing damaged neurons.
- Alzheimer's disease treatment: Replacing damaged brain cells.
Antigen Presenting Cells (APCs)
- APCs include dendritic cells, macrophages, and B lymphocytes.
- Occurrence: Found in the epithelium of the skin, GI tract, and respiratory tract, which are common entry points for microbes.
Functions of APCs
- Capture and transport antigens to peripheral lymphoid tissues
- Process antigens
- Present peptides derived from antigens to T lymphocytes
- APCs are rich in class II MHC molecules.
Role of Antigen Presenting Cells
- Phagocytosis: APCs phagocytose enemy cells (antigens).
- Fusion: Lysosomes fuse with phagosomes inside the APC.
- Degradation: Enzymes start to degrade the enemy cell.
- Fragmentation: The enemy cell is broken into small fragments.
- Presentation: Antigen fragments are presented on the APC surface.
- Exocytosis: Leftover fragments are released via exocytosis.
Pathways of Antigen Processing & Presentation
- Class II MHC Pathway:
- Protein antigens are taken from the extracellular environment.
- Proteins are degraded by lysosomal proteases.
- Resulting peptides are presented to CD4+ cells with class II MHC molecules.
- Class I MHC Pathway:
- Cytosolic proteins, such as those from intracellular microbes, are processed.
- Proteins are degraded by proteasomes.
- Resulting peptides are presented to CD8+ cells with class I MHC molecules.
Phagocytes
- Phagocytes are cells that recognize, ingest, and kill microbes and foreign bodies.
Types of Phagocytes
- Monocytes: Large mononuclear cells circulate in the blood and ingest microbes there.
- Macrophages: Tissue-resident cells derived from monocytes, ingest microbes in tissues.
- Neutrophils:
- Also called polymorphonuclear leukocytes (PMNs).
- Most numerous leukocytes in blood.
- Effective at killing bacteria.
- Increase in neutrophil count indicates acute infection.
- Ingest microbes in circulation, enter tissues at infection sites, and die after a few hours, contributing to pus formation.
Stages of Phagocytosis
- Delivery of phagocytic cell to site of infection:
- Diapedesis: Histamine stimulates phagocytes to migrate through blood vessel walls into tissues.
- Chemotaxis: Chemotactic factors like chemokines and complement components (C3a, C4a, C5a) attract phagocytes toward microbes in tissue.
- Recognition of microbes:
- Phagocytes recognize and bind microbes through receptors such as mannose receptors and Toll-Like receptors on their surface.
- Microbes coated with IgG or complement (C3b) enhance recognition
- IgG or C3b bind with receptors on phagocytic cells, bringing the microbe closer and facilitating phagocytosis.
- Opsonins Antibodies (IgG) or C3b enhance phagocytosis.
- Ingestion of target
- Phagocyte cell membrane invaginates to enclose the microbe, forming a vacuole called a phagosome.
- Phagolysosome formation
- The phagosome fuses with a lysosome, forming a phagolysosome.
- Intracellular killing
- Oxygen (O2)-dependent mechanisms (respiratory bursts):
- Production of O2 free radicals like H2O2, O2, and OH.
- Production of toxic nitrogen oxide.
- Oxygen (O2)-independent mechanisms:
- Lysosomal granules contain basic proteins that damage the permeability barrier of bacteria, fungi, and viruses.
- Lactoferrin chelates iron, reducing iron availability and bacterial growth.
- Lysosomal enzymes such as lysozyme and nuclease degrade microbes.
- Low pH due to lactic acid inhibits microbial growth.
- Oxygen (O2)-dependent mechanisms (respiratory bursts):
- Digestion
- Neutrophils: Short-lived and lyse after phagocytosis, contributing to pus.
- Macrophages:
- Egest digested debris.
- Digested microbes are processed into small antigen peptides presented on MHC to T helper cells.
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