Podcast
Questions and Answers
If a researcher discovers a novel leukocyte population exhibiting both rapid, non-specific cytotoxicity and antigen-presenting capabilities via MHC I and MHC II, alongside the expression of CD16 receptors, how would this cell type most accurately be classified, considering established immunological paradigms?
If a researcher discovers a novel leukocyte population exhibiting both rapid, non-specific cytotoxicity and antigen-presenting capabilities via MHC I and MHC II, alongside the expression of CD16 receptors, how would this cell type most accurately be classified, considering established immunological paradigms?
- A previously undocumented subtype of dendritic cell, derived from a plasmacytoid precursor, that has acquired cytotoxic function through epigenetic modification in response to chronic viral exposure.
- A hybrid innate-adaptive lymphocyte exhibiting characteristics of both natural killer cells and unconventional T cells, arising from a unique thymic developmental pathway.
- A highly specialized macrophage variant exhibiting lymphoid characteristics due to aberrant cytokine signaling during hematopoiesis, resulting in the ectopic expression of CD16.
- A novel lineage of innate lymphoid cell (ILC) that has undergone functional plasticity, acquiring antigen-presenting machinery through chronic exposure to inflammatory stimuli and subsequent transcriptional reprogramming. (correct)
During an acute systemic bacterial infection, a complete blood count reveals a significant increase in circulating metamyelocytes and band neutrophils, alongside elevated levels of IL-8 and G-CSF. Which of the following mechanisms best explains this phenomenon, considering the homeostatic regulation of hematopoiesis?
During an acute systemic bacterial infection, a complete blood count reveals a significant increase in circulating metamyelocytes and band neutrophils, alongside elevated levels of IL-8 and G-CSF. Which of the following mechanisms best explains this phenomenon, considering the homeostatic regulation of hematopoiesis?
- Inhibition of neutrophil apoptosis in the bone marrow microenvironment caused by bacterial proteases, leading to the accumulation and subsequent release of immature neutrophils into the bloodstream.
- Selective expansion of myeloid-biased hematopoietic stem cells (HSCs) due to direct stimulation by bacterial lipopolysaccharide (LPS), resulting in a transient shift in lineage commitment towards granulopoiesis.
- Compromised splenic sequestration of immature neutrophils due to saturation of splenic red pulp macrophages with opsonized bacteria, resulting in overflow of metamyelocytes and band cells into the circulation.
- Emergency myelopoiesis triggered by TLR signaling in bone marrow stromal cells, leading to accelerated neutrophil differentiation and premature release into circulation, overriding normal quality control checkpoints. (correct)
A research team isolates a novel strain of bacteria that resists phagocytosis by macrophages. Further analysis reveals that the bacteria secrete a protein that inhibits the fusion of phagosomes with lysosomes. Which of the following cellular processes would be least affected by this bacterial virulence factor?
A research team isolates a novel strain of bacteria that resists phagocytosis by macrophages. Further analysis reveals that the bacteria secrete a protein that inhibits the fusion of phagosomes with lysosomes. Which of the following cellular processes would be least affected by this bacterial virulence factor?
- Production of reactive oxygen species (ROS) within the phagocyte.
- Antigen presentation via MHC class II molecules.
- Activation of the inflammasome.
- Antibody-dependent cellular cytotoxicity (ADCC). (correct)
In the context of chronic granulomatous disease (CGD), where NADPH oxidase activity is impaired, leading to defective ROS production in phagocytes, which compensatory mechanism would be least likely to contribute to pathogen control?
In the context of chronic granulomatous disease (CGD), where NADPH oxidase activity is impaired, leading to defective ROS production in phagocytes, which compensatory mechanism would be least likely to contribute to pathogen control?
A researcher is investigating the effects of a novel adjuvant on dendritic cell (DC) activation. The adjuvant binds to an unknown receptor on DCs, leading to enhanced T cell priming. Which of the following signaling pathways is least likely to be involved in this DC activation process?
A researcher is investigating the effects of a novel adjuvant on dendritic cell (DC) activation. The adjuvant binds to an unknown receptor on DCs, leading to enhanced T cell priming. Which of the following signaling pathways is least likely to be involved in this DC activation process?
Following a successful hematopoietic stem cell transplantation, a patient experiences a delayed recovery of NK cell function, specifically impaired antibody-dependent cellular cytotoxicity (ADCC). Which of the following factors is least likely to contribute to this impaired ADCC response?
Following a successful hematopoietic stem cell transplantation, a patient experiences a delayed recovery of NK cell function, specifically impaired antibody-dependent cellular cytotoxicity (ADCC). Which of the following factors is least likely to contribute to this impaired ADCC response?
A research team discovers a novel immunomodulatory drug that selectively inhibits the differentiation of monocytes into macrophages, while sparing other myeloid lineages. Which of the following downstream effects would be least expected in vivo following administration of this drug?
A research team discovers a novel immunomodulatory drug that selectively inhibits the differentiation of monocytes into macrophages, while sparing other myeloid lineages. Which of the following downstream effects would be least expected in vivo following administration of this drug?
A patient with a genetic defect exhibits impaired migration of neutrophils from the bloodstream into infected tissues. This defect is most likely due to a deficiency in which of the following molecules?
A patient with a genetic defect exhibits impaired migration of neutrophils from the bloodstream into infected tissues. This defect is most likely due to a deficiency in which of the following molecules?
Within the context of an evolving tumor microenvironment, which of the following scenarios would least likely represent a mechanism by which tumor cells evade NK cell-mediated cytotoxicity?
Within the context of an evolving tumor microenvironment, which of the following scenarios would least likely represent a mechanism by which tumor cells evade NK cell-mediated cytotoxicity?
A novel therapeutic approach aims to enhance phagocytosis in macrophages by modulating lipid raft composition on the cell surface. Which of the following interventions would least likely contribute to enhanced phagocytic efficiency?
A novel therapeutic approach aims to enhance phagocytosis in macrophages by modulating lipid raft composition on the cell surface. Which of the following interventions would least likely contribute to enhanced phagocytic efficiency?
In the context of sepsis, characterized by dysregulated inflammation and immune suppression, which of the following therapeutic interventions targeting phagocytes would be least likely to improve patient outcomes?
In the context of sepsis, characterized by dysregulated inflammation and immune suppression, which of the following therapeutic interventions targeting phagocytes would be least likely to improve patient outcomes?
A researcher is studying the role of Fc receptors in mediating antibody-dependent enhancement (ADE) of viral infection. Which of the following scenarios would least likely contribute to ADE?
A researcher is studying the role of Fc receptors in mediating antibody-dependent enhancement (ADE) of viral infection. Which of the following scenarios would least likely contribute to ADE?
A patient presents with recurrent bacterial infections and impaired wound healing. Further investigation reveals a defect in the production of reactive oxygen species (ROS) within phagocytes, but normal NADPH oxidase activity. Which of the following mechanisms is the least likely explanation for this discrepancy?
A patient presents with recurrent bacterial infections and impaired wound healing. Further investigation reveals a defect in the production of reactive oxygen species (ROS) within phagocytes, but normal NADPH oxidase activity. Which of the following mechanisms is the least likely explanation for this discrepancy?
During prolonged exposure to particulate matter (e.g., silica, asbestos), macrophages can undergo a phenotypic switch, adopting a pro-fibrotic phenotype. Which of the following factors is least likely to contribute to this macrophage polarization?
During prolonged exposure to particulate matter (e.g., silica, asbestos), macrophages can undergo a phenotypic switch, adopting a pro-fibrotic phenotype. Which of the following factors is least likely to contribute to this macrophage polarization?
A researcher aims to develop a novel vaccine strategy targeting intracellular pathogens by enhancing antigen presentation by macrophages. Which of the following approaches would be least likely to improve antigen presentation via MHC class II molecules?
A researcher aims to develop a novel vaccine strategy targeting intracellular pathogens by enhancing antigen presentation by macrophages. Which of the following approaches would be least likely to improve antigen presentation via MHC class II molecules?
Flashcards
Phagocytosis
Phagocytosis
The process of engulfing and degrading invading microorganisms and non-self antigens.
Phagocytes
Phagocytes
Cells that perform phagocytosis to eliminate invading microbes. Originate from pluripotent hematopoietic stem cells in the bone marrow.
Monocytes
Monocytes
White blood cells that circulate for one to two days before entering tissues and differentiating into macrophages.
Macrophages
Macrophages
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Pseudopodia
Pseudopodia
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Phagosome
Phagosome
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Lysosome
Lysosome
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Phagolysosome
Phagolysosome
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Leukocytes
Leukocytes
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Lymphocytes
Lymphocytes
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Neutrophils
Neutrophils
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Dendritic Cells
Dendritic Cells
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Natural Killer (NK) Cells
Natural Killer (NK) Cells
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Fc Receptors (FcRs)
Fc Receptors (FcRs)
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ADCC
ADCC
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Study Notes
- Phagocytosis is a process where cells engulf and degrade microorganisms and antigens.
Phagocytes
- Phagocytes eliminate invading microbes
- Pluripotent hematopoietic stem cells from bone marrow are the origin of phagocytes.
- Myeloid lineage cells differentiate into phagocytes.
- Phagocytes are differentiated by cytoplasmic granulation and multi-lobed nuclei
- Monocytes circulate and differentiate into tissue macrophages when entering a tissue
- Macrophages are larger than monocytes with greater cytoplasmic space.
- Both monocytes and macrophages phagocytize their environment to remove microbes and debris.
- Phagocytosis serves as a scavenger mechanism to remove harmful microbes and cellular debris.
Phagocytosis process
- A phagocyte binds a microorganism at PRRs or TLR4, complement, and Fc receptors.
- Microorganism is engulfed via pseudopodia.
- The internalized microorganism is contained within a phagosome.
- The phagosome fuses with lysosomes to form a phagolysosome for digestion
- Macrophages present digested parts on their surface
- Macrophages secrete cytokines to recruit other immune cells.
- Phagocytosis occurs throughout the body and is interconnected with the innate immune response and inflammation
- White blood cells (phagocytes) consume microorganisms to protect the body from infection.
- The phagocyte is attracted to chemicals from the pathogen and binds to it through receptors.
- The phagocyte ingests the microbe, encasing it in a vacuole.
- Lysosomes merge with the vacuole, and their enzymes kill and digest the pathogen.
- Indigestible remains are released from the cell
- White blood cells are in constant circulation for a rapid response.
Leukocytes (White Blood Cells)
- Leukocytes are involved in both innate and adaptive immunity
- Leukocytes include granulocytes (neutrophils, eosinophils, basophils), monocytes, and lymphocytes
- Innate immunity involves rapid, nonspecific responses employing neutrophils, macrophages, and dendritic cells
- Lymphocytes are for adaptive immunity
- B cells produce antibodies
- T cells include helper T cells (assist B cells) and cytotoxic T cells (destroy infected cells)
- Natural Killer (NK) cells provide a rapid, nonspecific response
Leukocyte Classification
- All blood borne cells originate from pluripotent hematopoietic stem cells and differentiate into myeloid and lymphoid lineages.
- Leukocytes are classified by the presence/absence of microscopic granules and the number of lobes in the cell nuclei.
- Eosinophils, basophils, and neutrophils are examples
- Neutrophils, monocytes, macrophages, dendritic cells, and NK cells are primary cells of innate immunity.
Monocytes and Macrophages
- Monocytes differentiate from myeloid precursors and are mononuclear without granules.
- Monocytes are found in circulation with a half-life of 8.5 hours.
- Macrophages enter tissues and remain for months, maintaining the same morphology as monocytes.
- Both monocytes and macrophages scavenge pathogens, remove debris, promote inflammation, and secrete cytokines.
- Macrophages are APCs (antigen-presenting cells) that activate T cells to facilitate adaptive immunity.
Neutrophils
- Neutrophils contain cytoplasmic granules and are multilobed when mature
- Mature neutrophils take two weeks from metamyelocyte stage
- Neutrophils (PMNs) make up about 60% of blood leukocytes
- PMNs actively phagocytize and kill microbes and eliminate debris.
- PMNs secrete cytokines and inflammatory mediators during infection
- PMN numbers rapidly increase during acute infection.
Dendritic Cells
- Dendritic cells can originate from myeloid or lymphoid lineages
- Dendritic cells are mononuclear without granules.
- Dendritic cells are found in the skin, lungs, and GI tract.
- Dendritic cells phagocytize and kill microbes and remove debris.
- Dendritic cells sample extracellular fluid to remove foreign material
- Dendritic cells are critical for B and T cell activation and regulation.
Natural Killer (NK) Cells
- NK cells originate from the lymphoid lineage and are non-phagocytic.
- NK cells are mononucleated with granules, making up 5-10% of lymphocytes.
- NK cells recognize and destroy virally infected and tumor cells.
- NK cells eliminate virus-infected and tumor cells.
- NK cells have CD16 receptors that recognize antibodies
- NK cells bind IgE, IgG, and IgA on opsonized bacteria, protozoa, and parasitic worms.
- NK cells inject granules containing cytotoxic agents to destroy the microbe
- This killing mechanism is antibody-dependent cell-mediated cytotoxicity
Fc Receptors (FcRs)
- Fc receptors allow immune cells to recognize and interact with antibodies
- Fc receptors trigger phagocytosis when they bind to antibodies that have opsonized pathogens, known as antibody-dependent cellular phagocytosis (ADCP).
- Fc receptors on NK cells enable the cells to kill antibody-coated cells, such as infected or tumor cells, known as (ADCC).
- Fc receptor engagement can trigger immune cell activation, leading to the secretion of cytokines, inflammatory mediators, and other substances
- These are abundant phagocytes that express Fc receptors for IgG (FcgRs)
- Binding of IgG-coated pathogens enhances phagocytosis and microbial killing.
- Macrophages express Fc receptors (including FcgRs and FceRs) .
- The receptors bind to antibody-coated pathogens, promoting phagocytosis and activating inflammatory responses.
- Dendritic cells use Fc receptors to capture antibody-coated pathogens and present them to T cells, linking the innate to adaptive immunity.
- NK cells express Fc receptors, particularly FcγRIII (CD16), which allows them to recognize and kill antibody-coated target cells through ADCC.
- Eosinophils and Basophils: These cells have Fc receptors for IgE, specifically FceRs, and are involved in allergic reactions and defense against parasitic infections.
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Description
Phagocytosis is a process where cells engulf and degrade microorganisms and antigens. Phagocytes eliminate invading microbes and differentiate from myeloid lineage cells. They bind microorganisms, engulf them via pseudopodia, and contain them within a phagosome, which fuses with lysosomes to form a phagolysosome.
