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cells of the immune system
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cells of the immune system

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Questions and Answers

Which function is primarily associated with eosinophils?

  • Releasing histamines to combat allergies
  • Engulfment of dead cells
  • Bacterial phagocytosis
  • Anti-parasitic activity (correct)

    • What types of reactive intermediates are involved in the oxygen-dependent killing of bacteria by neutrophils?

  • Defensins and lysozymes
  • Cytokines and histamines
  • Hydrolytic enzymes alone
  • Reactive oxygen and nitrogen species (correct)

    • What is the typical size range of eosinophils in diameter?

  • 18-25 μm
  • 12-17 μm (correct)
  • 10-15 μm
  • 5-10 μm

    • Which component is NOT part of the oxygen-independent mechanisms of bacterial killing?

    <p>Reactive nitrogen intermediates</p> Signup and view all the answers

    What type of granules do eosinophils contain?

    <p>Spherical eosinophilic granules</p> Signup and view all the answers

    Which type of white blood cells is formed through granulopoiesis?

    <p>Neutrophils</p> Signup and view all the answers

    What is a characteristic feature of hematopoietic stem cells?

    <p>They can self-renew and differentiate into multiple lineages.</p> Signup and view all the answers

    Where does hematopoiesis primarily occur in adults?

    <p>Bone marrow</p> Signup and view all the answers

    Which hematopoietic growth factor is involved in granulocyte maturation?

    <p>Granulocyte monocyte – colony stimulating factor (GM-CSF)</p> Signup and view all the answers

    What is the lifespan of neutrophils after they migrate into tissues?

    <p>48 hours</p> Signup and view all the answers

    Which of the following describes the morphology of neutrophils?

    <p>Segmented nucleus typically with 3-4 segments.</p> Signup and view all the answers

    What is one of the primary functions of neutrophils?

    <p>Phagocytosis of bacteria.</p> Signup and view all the answers

    Hematopoiesis in a fetus mainly occurs in which locations during the first few months?

    <p>Yolk sac, liver, and spleen.</p> Signup and view all the answers

    What is a primary function of eosinophils in the immune response?

    <p>Anti-parasitic function</p> Signup and view all the answers

    Which type of reactive intermediates is specifically associated with oxygen-dependent bacterial killing?

    <p>Nitric oxide</p> Signup and view all the answers

    In which location are eosinophils especially prevalent?

    <p>Small intestine</p> Signup and view all the answers

    What morphological feature is characteristic of eosinophils?

    <p>Segmented nucleus with two nuclear lobes</p> Signup and view all the answers

    What cytokine-related function do eosinophils provide in the immune system?

    <p>Instruct adaptive immune responses</p> Signup and view all the answers

    What are the characteristics of hematopoietic stem cells (HSC)?

    <p>They possess self-renewal and multilineage differentiation potential.</p> Signup and view all the answers

    Which of the following statements is true regarding granulocyte maturation?

    <p>Granulopoiesis results in the formation of neutrophils, eosinophils, and basophils.</p> Signup and view all the answers

    In which anatomical sites does hematopoiesis occur during infancy?

    <p>In almost all bones through bone marrow.</p> Signup and view all the answers

    Which type of immune response is primarily assisted by neutrophils?

    <p>Phagocytosis and initial response to infections.</p> Signup and view all the answers

    How do hematopoietic growth factors function?

    <p>They can show synergistic or additive actions with other growth factors.</p> Signup and view all the answers

    What is the approximate diameter of neutrophils?

    <p>13 μm</p> Signup and view all the answers

    Which of the following is NOT a characteristic of granulocytes?

    <p>They have a long lifespan in circulation.</p> Signup and view all the answers

    What is the role of chemokines in the function of neutrophils?

    <p>They assist in the migration of neutrophils to sites of infection.</p> Signup and view all the answers

    Immune cells arise from pluripotent hematopoietic stem cells in the ______.

    <p>bone marrow</p> Signup and view all the answers

    The formation of red blood cells is known as ______.

    <p>erythropoiesis</p> Signup and view all the answers

    Granulocytes are formed through a process called ______.

    <p>granulopoiesis</p> Signup and view all the answers

    The lifespan of neutrophils after migrating into tissues is approximately ______.

    <p>48 hours</p> Signup and view all the answers

    Hematopoiesis in adults primarily occurs in the ______.

    <p>bone marrow</p> Signup and view all the answers

    Monocytes develop into ______ after their maturation process.

    <p>macrophages</p> Signup and view all the answers

    Hematopoietic growth factors act at low ______.

    <p>concentrations</p> Signup and view all the answers

    Most abundant leukocytes in circulation are called ______.

    <p>neutrophils</p> Signup and view all the answers

    Dead neutrophils accumulate as the major cell type in ______.

    <p>pus</p> Signup and view all the answers

    Eosinophils are primarily involved in anti-______ function.

    <p>parasitic</p> Signup and view all the answers

    The frequency of eosinophils in circulation is approximately ______% of leukocytes.

    <p>1-3</p> Signup and view all the answers

    Eosinophils release ______ to instruct adaptive immune responses.

    <p>cytokines</p> Signup and view all the answers

    Eosinophils contain an anti-parasite protein called ______.

    <p>eosinophil cationic protein (ECP)</p> Signup and view all the answers

    Study Notes

    Hematopoiesis

    • The process of creating red blood cells (erythrocytes) and white blood cells (leukocytes)
    • All leukocytes originate from hematopoietic stem cells (HSCs) in the bone marrow

    Hematopoietic Stem Cells

    • They possess self-renewal and multi-lineage differentiation potential (pluripotent)
    • Less than 1 in 50,000 bone marrow cells are HSCs
    • Maintained at steady-state levels throughout adulthood
    • Possess remarkable proliferative capacity, with as little as 10% of a donor’s hematopoietic system potentially regenerating the entire system in a bone marrow transplant recipient

    Hematopoiesis Site Variations by Age

    • Fetus:
      • Yolk sac: 0-2 months
      • Liver and spleen: 2-7 months
      • Bone marrow: 5-9 months
    • Infants: Bone marrow in practically all bones
    • Adults: Bone marrow (Vertebrae, ribs, sternum, skull, sacrum, pelvis, and the end of femurs)

    Hematopoietic Growth Factors

    • Glycoproteins that act at low concentrations
    • Produced by various cells: stromal cells, monocytes, and lymphocytes
    • Can influence multiple cell lineages
    • Exhibit synergistic or additive effects with other growth factors
    • Active on stem cells and/or functional end cells
    • Have multifaceted actions
    • Examples: Stem cell factor (SCF), granulocyte monocyte – colony stimulating factor (GM-CSF), and various interleukins (IL-3, IL-5, IL-6, IL-7, IL-11, IL-15)

    Granulocytes – Neutrophils

    • Most abundant leukocyte (50-70% in circulation)
    • Remain in circulation for 7-10 hours before migrating into tissues
    • Life span in tissues: ~48 hours
    • Highly responsive to infection, often the first responders, and are recruited to infection sites by chemokines - inflammatory molecules
    • Morphology:
      • Segmented nucleus (3-4 nuclear segments) connected by tapering chromatin strands – polymorphonuclear leukocyte (PMN).
      • Primary granules (larger, denser; lysosomal function).
      • Secondary granules (smaller).
      • Size – approximately 13 μm in diameter

    Granulocytes – Neutrophil Functions

    • Phagocytosis (engulfment) of bacteria
    • Secrete proteins for bacterial killing and tissue remodeling signaling
    • Contribute to shaping the adaptive immune response when needed
    • Accumulate as the main cell type in pus upon death

    Granulocytes – Neutrophil Bacterial Killing

    • Oxygen-dependent:
      • Reactive oxygen intermediates (anion, hydroxyl radical, hydrogen peroxide, hypochlorite anion)
      • Reactive nitrogen intermediates (nitric oxide)
    • Oxygen-independent:
      • Defensins
      • Lysozyme
      • Hydrolytic enzymes
      • Tumor necrosis factor

    Granulocytes – Eosinophils

    • Frequency in circulation: 1-3% of leukocytes
    • Circulate through the blood and into the tissues
    • Especially prevalent in the small intestine
    • Morphology:
      • Segmented nucleus (2 nuclear lobes) – PMN leukocyte.
      • Spherical granules (eosinophilic granules).
      • Size – approximately 12-17 μm in diameter.

    Granulocytes – Eosinophil Functions

    • Anti-parasitic function, also involved in allergy and asthma
    • Release cytokines to guide adaptive immune responses, coordinating immune responses, particularly against multicellular parasites (i.e. worms).
    • Possess lysosomal and oxygen-radical generation enzymes akin to neutrophils.
    • Contain an anti-parasite protein called eosinophil cationic protein (ECP).

    Granulocytes - Basophils

    • Frequency in circulation: not provided in text

    Hematopoiesis

    • The process of blood cell formation and development
    • Hematopoietic stem cells (HSCs) are the origin of all blood cells
    • HSCs are found in bone marrow
    • HSCs can self-renew and differentiate into various blood cell lineages

    Leukocyte Formation

    • Granulocytes:
      • Neutrophils, eosinophils, basophils, and mast cells
      • Process called granulopoiesis
    • Monocytes:
      • Monocytes, macrophages, and dendritic cells
      • Process called monocytopoiesis
    • Lymphocytes:
      • T cells, B cells, natural killer (NK) cells, and NKT cells
      • Process called lymphopoiesis

    Hematopoietic Stem Cell Characteristics

    • Self-renewal: Ability to produce more stem cells
    • Multilineage differentiation: Potential to become any blood cell type
    • Scarce: Less than 1 in 50,000 bone marrow cells
    • Sustained: Maintained throughout adulthood
    • Proliferative: Can repopulate an entire hematopoietic system from a small donor sample

    Sites of Hematopoiesis

    • Fetus:
      • Yolk sac (0-2 months)
      • Liver and spleen (2-7 months)
      • Bone marrow (5-9 months)
    • Infants: Bone marrow in all bones
    • Adults: Bone marrow in specific bones like vertebrae, ribs, sternum, skull, sacrum, pelvis, and ends of femurs

    Hematopoietic Growth Factors

    • Glycoproteins that regulate blood cell production
    • Produced by various cells like stromal cells, monocytes, and lymphocytes
    • Affect multiple cell lineages
    • Synergistic or additive effects
    • Act on stem cells or mature blood cells
    • Examples: Stem cell factor, granulocyte monocyte-colony stimulating factor (GM-CSF), and interleukins (IL-3, IL-5, IL-6, IL-7, IL-11, IL-15)

    Granulocyte - Neutrophil

    • Most abundant leukocyte (50-70% in circulation)
    • Short lifespan in circulation (7-10 hours)
    • Migrate to tissues to fight infection (lifespan ~48 hours)
    • First responders to infection
    • Morphology:
      • Segmented nucleus (3-4 lobes)
      • Polymorphonuclear leukocyte (PMN)
      • Primary granules (larger, lysosomal function)
      • Secondary granules (smaller)
      • Size: 13 μm in diameter

    Neutrophil Functions

    • Phagocytosis (engulfment of bacteria)
    • Secretes proteins to kill bacteria and initiate tissue repair
    • Contributes to adaptive immune response
    • Accumulates in pus (dead neutrophils)

    Neutrophil Mechanisms for Killing Bacteria

    • Oxygen-dependent:
      • Reactive oxygen intermediates (anion, hydroxyl radical, hydrogen peroxide, hypochlorite anion)
      • Reactive nitrogen intermediates (nitric oxide)
    • Oxygen-independent:
      • Defensins, lysozyme, hydrolytic enzymes, tumor necrosis factor

    Granulocyte - Eosinophil

    • Less common leukocyte (1-3% in circulation)
    • Found in blood and tissues, especially the small intestine
    • Morphology:
      • Segmented nucleus (2 lobes)
      • PMN leukocyte
      • Spherical granules (eosinophilic granules)
      • Size: 12-17 μm in diameter
    • Key role in anti-parasitic function
    • Involved in allergic reactions and asthma
    • Releases cytokines to instruct the adaptive immune system
    • Contains lysosomal and oxygen-radical generating enzymes
    • Contains eosinophil cationic protein (ECP) for killing parasites

    Granulocyte - Basophil

    • Least common leukocyte (less than 1%)
    • Circulate in blood and enter tissues
    • Morphology:
      • Segmented nucleus (often obscured by granules)
      • PMN leukocyte
      • Large, irregularly shaped granules
      • Size: 10-14 μm in diameter
    • Important in allergic reactions
    • Contains histamine and other mediators of inflammation
    • Releases cytokines and chemokines
    • Releases heparin (anticoagulant)
    • Plays a role in immune responses to parasites

    Granulocyte - Mast Cell

    • Reside in tissues
    • Not in circulation
    • Morphology:
      • Large, irregularly shaped granules
      • Varying size (15-30 μm)
    • Important in allergic reactions
    • Contain histamine and other inflammatory mediators
    • Releases cytokines and chemokines in response to allergens
    • Plays a role in tissue repair and defense against parasites

    Hematopoiesis

    • The process of forming and developing red blood cells (erythrocytes) and white blood cells (leukocytes).
    • All leukocytes originate from hematopoietic stem cells in the bone marrow.

    Leukocyte Development

    • Granulocytes:
      • Neutrophils, eosinophils, basophils, and mast cells develop through granulopoiesis.
    • Monocytes:
      • Monocytes, macrophages, and dendritic cells develop through monocytopoiesis.
    • Lymphocytes:
      • T cells, B cells, natural killer (NK) cells, and NKT cells develop through lymphopoiesis.

    Hematopoietic Stem Cells (HSCs)

    • Self-renewing cells with the potential to differentiate into all blood cell types (pluripotent).
    • Rare, representing fewer than 1 in 50,000 bone marrow cells.
    • Maintain steady-state levels throughout adulthood.
    • Possess significant proliferative capacity, capable of regenerating the entire hematopoietic system in a bone marrow transplant patient.

    Hematopoiesis Sites Across Lifespan

    • Fetus:
      • Yolk sac (0-2 months)
      • Liver and spleen (2-7 months)
      • Bone marrow (5-9 months)
    • Infants:
      • Bone marrow in virtually all bones.
    • Adults:
      • Bone marrow in specific bones: vertebrae, ribs, sternum, skull, sacrum, pelvis, and ends of femurs.

    Hematopoietic Growth Factors

    • Glycoproteins that influence hematopoiesis at low concentrations.
    • Produced by various cells including stromal cells, monocytes, and lymphocytes.
    • Often have effects on multiple cell lineages.
    • Can act synergistically or additively with other growth factors.
    • Influence both stem cells and functional end cells.
    • Examples: Stem cell factor (SCF), granulocyte monocyte – colony stimulating factor (GM-CSF), and various interleukins (IL-3, IL-5, IL-6, IL-7, IL-11, IL-15).

    Granulocyte: Neutrophil

    • Most abundant leukocyte (50-70% in circulation).
    • Short lifespan in circulation (7-10 hours) before migrating into tissues, where they survive for ~48 hours.
    • Rapidly respond to infection, often the first responders, and migrate towards infection sites guided by chemokines (inflammatory molecules).

    Neutrophil Morphology

    • Segmented nucleus (typically 3-4 segments) connected by thin chromatin strands – polymorphonuclear leukocyte (PMN).
    • Primary granules (larger, denser; lysosomal function).
    • Secondary granules (smaller).
    • Size: approximately 13 μm in diameter.

    Neutrophil Functions

    • Phagocytosis (engulfment) of bacteria.
    • Release proteins to kill bacteria and initiate tissue repair.
    • Influence the adaptive immune response when needed.
    • Accumulate as the primary cell type in pus.

    Neutrophil Mechanisms of Bacterial Killing

    • Oxygen-dependent:
      • Reactive oxygen intermediates (superoxide anion, hydroxyl radical, hydrogen peroxide, hypochlorite anion), and reactive nitrogen intermediates (nitric oxide).
    • Oxygen-independent:
      • Defensins, lysozyme, hydrolytic enzymes, tumor necrosis factor.

    Granulocyte: Eosinophil

    • Present at 1-3% of leukocytes in circulation.
    • Circulate in the blood and migrate into tissues.
    • Highly concentrated in the small intestine.

    Eosinophil Morphology

    • Segmented nucleus (2 lobes) – PMN leukocyte.
    • Spherical granules (eosinophilic granules).
    • Size: approximately 12-17 μm in diameter.

    Eosinophil Functions

    • Primarily involved in anti-parasitic defense, but also contribute to allergic reactions and asthma.
    • Release cytokines to guide adaptive immune responses, particularly against multicellular parasites (e.g., worms).
    • Contain lysosomal and oxygen-radical generating enzymes similar to neutrophils.
    • Express an anti-parasite protein called eosinophil cationic protein (ECP).

    Granulocyte: Basophil

    • The least abundant leukocyte in circulation.
    • Play a crucial role in allergic reactions.
    • Contain histamine and heparin granules, which are released upon activation.
    • These granules contribute to the inflammatory response and blood vessel dilation.
    • Release chemokines and cytokines (e.g., IL-4 and IL-13), which promote allergic inflammation.

    Mast Cells

    • Reside in various tissues, including the skin, mucous membranes, and connective tissues.
    • Play a central role in allergic reactions, inflammatory responses, and defense against parasites.
    • Similar to basophils, they contain histamine and heparin granules, which are released upon activation.
    • They also produce cytokines and chemokines, contributing to inflammation.

    Monocyte

    • Represent 5-10% of leukocytes in circulation.
    • Large, phagocytic cells that differentiate into macrophages or dendritic cells.
    • They contribute to innate immunity through phagocytosis of pathogens and debris.
    • They present antigens to T cells, bridging innate and adaptive immunity.

    Macrophage

    • Highly phagocytic cells that develop from monocytes.
    • Reside in various tissues and contribute to tissue repair and defense against infections.
    • Phagocytize pathogens, dead cells, and other debris.
    • Release cytokines and chemokines to modulate inflammation and recruit other immune cells.
    • Present antigens to T cells, linking innate and adaptive immunity.

    Dendritic Cell

    • Antigen-presenting cells that bridge innate and adaptive immunity.
    • Found in various tissues, including skin, mucous membranes, and lymphoid organs.
    • Specialize in capturing and displaying antigens to T cells.
    • Produce cytokines that shape the adaptive immune response.

    Lymphocyte

    • Represent 20-40% of leukocytes in circulation.
    • Responsible for adaptive immune responses.
    • Two main types: T cells and B cells.
    • T cells:
      • Coordinate and execute cellular immune responses.
      • Recognize and destroy infected cells or tumor cells.
      • Secrete cytokines to regulate immune responses.
    • B cells:
      • Produce antibodies, circulating proteins that specifically bind to antigens.
      • Play a crucial role in humoral immunity, defending against extracellular pathogens.

    Natural Killer (NK) Cells

    • Large granular lymphocytes that contribute to innate immunity.
    • Eliminate infected or cancerous cells without prior sensitization to specific antigens.
    • Utilize a variety of mechanisms to kill target cells, including cytotoxic granules and activating receptors.

    NKT Cells

    • A hybrid of NK and T cells, expressing both NK cell receptors and T cell receptors.
    • Respond rapidly to various pathogens, including bacteria, viruses, and parasites.
    • Secrete cytokines, including IFN-γ, which activate other immune cells.

    Red Blood Cells (Erythrocytes)

    • Develop through erythropoiesis.
    • Transport oxygen throughout the body.
    • Lack a nucleus and other organelles.
    • Contain hemoglobin, a protein that binds to oxygen.

    Platelets (Thrombocytes)

    • Develop through thrombopoiesis.
    • Small, anuclear cells that contribute to blood clotting.
    • Release factors that promote coagulation and platelet aggregation, forming a clot to stop bleeding.

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    Explore the intricate process of hematopoiesis, which involves the creation of red and white blood cells from hematopoietic stem cells. This quiz covers the variations of hematopoiesis across different age groups and the role of hematopoietic growth factors. Test your understanding of how blood cell formation is maintained and regulated throughout life.

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