Hematopoiesis Stem Cell Differentiation
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Questions and Answers

Which transcription factor plays a crucial role in the lymphoid lineage?

  • GATA2
  • PU.1
  • STAT5
  • Ikaros (correct)

    • What regulates the levels and types of cytokines produced by bone-marrow stromal cells?

  • Hematopoietic stem cells
  • Hematopoietic progenitor cells
  • Stromal cells themselves (correct)
  • T cells and macrophages

    • What is the term for the ordered process of cell death, in which the cell actively participates in its own demise?

  • Necrosis
  • Autophagy
  • Mitosis
  • Apoptosis (correct)

    • What is the primary function of macrophages in relation to apoptotic cells?

    <p>To phagocytose and remove apoptotic cells</p> Signup and view all the answers

    What is a characteristic morphologic change associated with apoptosis?

    <p>Modification of the cytoskeleton resulting in membrane blebbing</p> Signup and view all the answers

    What is the fate of the DNA in cells undergoing apoptosis?

    <p>It is degraded into smaller fragments</p> Signup and view all the answers

    What is a key difference between apoptosis and necrosis?

    <p>Apoptosis is an orderly process, while necrosis is not</p> Signup and view all the answers

    What is the term for the small, membrane-bound structures that contain intact organelles and are shed by apoptotic cells?

    <p>Apoptotic bodies</p> Signup and view all the answers

    What is the typical life span of effector cells?

    <p>A few days to a few weeks</p> Signup and view all the answers

    What percentage of lymphocytes are Natural Killer cells?

    <p>5%–10%</p> Signup and view all the answers

    How do Natural Killer cells recognize target cells?

    <p>Through Killer Inhibitory Receptor and CD16</p> Signup and view all the answers

    What is the primary function of activated B cells?

    <p>Antibody production</p> Signup and view all the answers

    What triggers the differentiation of B cells into plasma cells?

    <p>Antigen binding to surface IgM molecules</p> Signup and view all the answers

    What is unique about the process of B-cell activation?

    <p>It is the most efficient presenting cell in the body</p> Signup and view all the answers

    What happens to lymphocytes as they progress through the cell cycle?

    <p>They enlarge into blast cells with higher cytoplasm:nucleus ratio</p> Signup and view all the answers

    What is the term for B and T lymphocytes that have not interacted with antigen?

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

    What determines the differentiation of a stem cell or progenitor cell?

    <p>The amount of growth factors in the microenvironment</p> Signup and view all the answers

    What is the main function of stromal cells in bone marrow?

    <p>To support the growth and differentiation of HSCs</p> Signup and view all the answers

    What is the result of hematopoietic stem cells differentiating into progenitor cells?

    <p>They lose the capacity for self-renewal</p> Signup and view all the answers

    What is the role of stromal cells in regulating hematopoiesis during infection?

    <p>They produce hematopoietic growth factors</p> Signup and view all the answers

    What is required for the development of pluripotent HSCs into different cell types?

    <p>The expression of different sets of lineage-determining and lineage-specific genes</p> Signup and view all the answers

    What is the function of hematopoietic growth factors?

    <p>To promote the growth and differentiation of HSCs</p> Signup and view all the answers

    What is the result of hematopoietic stem cells differentiating along one of two pathways?

    <p>They give rise to either common lymphoid or common myeloid progenitor cells</p> Signup and view all the answers

    What is the role of the proteins specified by lineage-determining and lineage-specific genes?

    <p>They are critical components of regulatory networks that direct the differentiation of HSCs</p> Signup and view all the answers

    What is the role of neutrophils in the body?

    <p>To serve as the first line of defense in inflammation</p> Signup and view all the answers

    Which of the following cell types is involved in parasitic infections?

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

    What is a characteristic of lymphocytes?

    <p>They possess the attributes of diversity, specificity, memory, and self/nonself recognition</p> Signup and view all the answers

    What is the role of myeloid cells in the immune response?

    <p>To serve as the first line of defense in non-specific innate immunity</p> Signup and view all the answers

    What is the main function of basophils in the body?

    <p>To participate in Type I hypersensitivity responses</p> Signup and view all the answers

    What is the result of cellular necrosis?

    <p>The cell swells and bursts, releasing its contents and possibly triggering a damaging inflammatory response</p> Signup and view all the answers

    What is the function of eosinophils in the body?

    <p>To mediate toxic reactions to large parasites</p> Signup and view all the answers

    Which of the following is NOT a characteristic of lymphocytes?

    <p>They are the first line of defense in inflammation</p> Signup and view all the answers

    What is the function of CD40 on B cells?

    <p>Co-stimulatory molecule</p> Signup and view all the answers

    Which of the following molecules is NOT a signal transduction molecule on B cells?

    <p>HLA-D</p> Signup and view all the answers

    What is the function of CD19 on B cells?

    <p>B-cell co-receptor subunit</p> Signup and view all the answers

    Which of the following T cells are involved in cell-mediated immunity?

    <p>Both T helper and cytotoxic T cells</p> Signup and view all the answers

    What is the function of CD28 on T cells?

    <p>Co-stimulatory molecule</p> Signup and view all the answers

    Which of the following molecules is a T cell receptor complex component?

    <p>CD3</p> Signup and view all the answers

    What is the function of T helper cells (Th)?

    <p>All of the above</p> Signup and view all the answers

    Which of the following molecules is a marker for naive T cells?

    <p>CD45RA</p> Signup and view all the answers

    Study Notes

    Hematopoiesis

    • A multipotent stem cell differentiates into either a common lymphoid progenitor cell or a common myeloid progenitor cell
    • The types and amounts of growth factors in the microenvironment of a stem cell or progenitor cell control its differentiation
    • During lymphoid and myeloid lineage development, stem cells differentiate into progenitor cells, which lose self-renewal capacity and commit to a particular cell lineage

    Stromal Cells and the Microenvironment

    • In bone marrow, HSCs grow and mature on a meshwork of stromal cells, which are nonhematopoietic cells that support HSC growth and differentiation
    • Stromal cells include fat cells, endothelial cells, fibroblasts, and macrophages
    • Stromal cells influence HSC differentiation by providing a hematopoietic-inducing microenvironment (HIM) consisting of a cellular matrix and growth factors

    Hematopoietic Growth Factors

    • Hematopoietic growth factors are soluble agents that arrive at target cells by diffusion or membrane-bound molecules on stromal cells that require cell-to-cell contact
    • During infection, hematopoiesis is stimulated by the production of hematopoietic growth factors by activated macrophages and T cells

    Hematopoiesis Regulation

    • Hematopoiesis is regulated at the genetic level
    • The development of pluripotent HSCs into different cell types requires the expression of different sets of lineage-determining and lineage-specific genes at appropriate times and in the correct order
    • Transcription factors such as GATA2 and Ikaros play important roles in hematopoiesis

    Hematopoietic Homeostasis

    • Steady-state regulation of hematopoiesis is accomplished through various mechanisms, including:
      • Control of cytokine levels and types produced by bone marrow stromal cells
      • Production of cytokines with hematopoietic activity by other cell types, such as activated T cells and macrophages
      • Regulation of receptor expression for hematopoietically active cytokines in stem cells and progenitor cells
      • Removal of cells by controlled induction of cell death

    Programmed Cell Death (Apoptosis)

    • Apoptosis is an induced and ordered process in which cells actively participate in bringing about their own demise
    • Morphologic changes in apoptosis include:
      • Decreased cell volume
      • Modification of the cytoskeleton resulting in membrane blebbing
      • Condensation of chromatin
      • Degradation of DNA into smaller fragments
    • Apoptotic cells are phagocytosed by macrophages, preventing inflammation

    Leukocytes

    • White blood cells that provide either innate or specific adaptive immunity
    • Myeloid cells: first line of defense, non-specific innate immunity
      • Neutrophils
      • Eosinophils
      • Basophils/Mast cells
      • Monocytes/Macrophages/Dendritic cells
    • Lymphoid cells:
      • Non-specific immunity
        • Natural Killer cells
      • Humoral and Cell-Mediated specific immunity
        • B Lymphocytes
        • T Lymphocytes (Helper and Cytolytic)

    Neutrophils

    • Produced in the bone marrow from myeloblast-type stem cells
    • Main role is in inflammation
    • First cells to arrive at the site of inflammation by leaving the blood vessels (extravasation)
    • Attracted by chemotactic factors, including complement proteins, clotting proteins, and T cell-derived cytokines

    Eosinophils

    • Granulocytes that stain intensely with 'eosin'
    • Bilobed nucleus
    • Contain basic crystal granules in cytoplasm that mediate toxic reactions to large parasites
    • Involved in asthma and parasitic infections

    Basophils

    • Found in low numbers in the blood
    • Act like mast cells
    • Involved in Type I hypersensitivity responses
    • Have high-affinity Fc receptors for IgE on their surface

    Lymphoid Leukocytes

    • B cells, T cells, and natural killer cells
    • B and T lymphocytes that have not interacted with antigen are referred to as naive or unprimed
    • Interaction with antigen induces cells to enter the cell cycle and differentiate into effector cells or memory cells

    B Lymphocytes

    • Develop from stem cells in the bone marrow
    • Produce antibodies with specificity for antigens
    • Plasma cells are activated B cells
    • Upon activation, a B cell can switch to produce a different class of antibody with the same antigen specificity

    T Lymphocytes

    • Regulate immune responses
    • Integral in cell-mediated immunity
    • Critical in B cell-antibody production
    • Mature T cells display either CD4 or CD8
    • Develop in the thymus
    • Cells with a CD4 marker are called helper T cells (Th cells)
    • Cells with a CD8 marker are cytotoxic T cells (Tc cells)
    • Each T cell has a TCR to recognize antigen

    Surface Molecules of T Lymphocytes

    • TCR, T cell receptor
    • CD3, TCR signaling complex
    • Thy-1, mouse T cell marker
    • CD45RO, Leukocyte common antigen for memory T cells
    • CD45RA, Leukocyte common antigen for naive T cells
    • CD2, LFA-3 adhesion molecule
    • CD28, co-stimulatory molecule that binds B7
    • CD5, co-stimulatory molecule
    • CD7, signal transduction

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    Quiz about the differentiation of multipotent stem cells in hematopoiesis, including the role of growth factors and the development of lymphoid and myeloid lineages.

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