Neutrophil Granules
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Questions and Answers

What type of stain is used to differentiate myeloid precursors from lymphoid precursors?

Sudan black B

What is the function of terminal deoxynucleotidyl transferase (TdT) in cells?

A specialized DNA polymerase expressed in immature, pre-B, pre-T lymphoid cells, and acute lymphoblastic leukemia/lymphoma cells

What is the purpose of the periodic acid-Schiff (PAS) stain in cell analysis?

To detect glycogen in cells

What CD markers are present on neutrophils?

<p>CD15, CD16, and CD11b/CD18</p> Signup and view all the answers

What is the sequence of neutrophil granule formation during granulopoiesis?

<p>Azurophilic or primary granules, specific or secondary granules, and then gelatinase or tertiary granules</p> Signup and view all the answers

What is the final stage of neutrophil maturation?

<p>Formation of secretory vesicles (SVs)</p> Signup and view all the answers

In which type of leukemia does DNA polymerase stain positive?

<p>Erythroid leukemia (M6)</p> Signup and view all the answers

What is the function of neutrophils in hypoxic conditions?

<p>Obtain energy by glycolysis, utilizing glycogen</p> Signup and view all the answers

What is the average time spent by neutrophils in tissues before they are destroyed during defensive action or as a result of senescence?

<p>4-5 days</p> Signup and view all the answers

What triggers the expression of adhesion molecules on endothelial cells and neutrophils?

<p>Exposure to chemoattractants</p> Signup and view all the answers

What is the purpose of the b2 integrins expressed on neutrophils in Stage 2 of leukocyte extravasation?

<p>To attach to ICAMs on endothelial cells</p> Signup and view all the answers

What is the result of the attachment of b2 integrins to ICAMs in Stage 3 of leukocyte extravasation?

<p>A firmer attachment and halting of rolling, leading to cellular migration</p> Signup and view all the answers

What is the direction of movement of neutrophils during chemotaxis?

<p>Towards the chemoattractants</p> Signup and view all the answers

What structures do neutrophils use to squeeze through endothelial cells during diapedesis?

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

What are the mediators that activate endothelial cells and neutrophils, leading to leukocyte extravasation?

<p>Chemoattractants, including C5a, bacterial products, lipid mediators, and chemokines</p> Signup and view all the answers

What is the process by which neutrophils move through the endothelium and basement membrane to the area of inflammation?

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

What are the two types of granules found in neutrophils, and in which stages of cell maturity are they typically found?

<p>Primary (azurophilic) granules in young cells, and secondary (specific) granules in more mature cells.</p> Signup and view all the answers

What is the function of myeloperoxidase in neutrophils?

<p>To generate toxic bacteria-killing substances, specifically hypochlorous acid.</p> Signup and view all the answers

What is the role of elastase in neutrophils?

<p>To break down elastin, a protein found in connective tissues, aiding in tissue penetration and facilitating the immune response.</p> Signup and view all the answers

What is the function of cationic proteins and defensins in primary granules?

<p>To disrupt microbial cell membrane integrity, contributing to the elimination of pathogens.</p> Signup and view all the answers

What are the multiple functions of cathepsin G?

<p>To clear pathogens, regulate inflammation, modify chemokines and cytokines, control blood pressure, and induce thrombogenesis.</p> Signup and view all the answers

What is the function of lysozyme in neutrophils?

<p>To break down bacterial cell walls.</p> Signup and view all the answers

What are the functions of Bacterial Permeability Increasing Protein (BPI)?

<p>Bactericidal and lipopolysaccharide-neutralizing activities, and promotion of complement activation on bacterial surfaces.</p> Signup and view all the answers

What is the function of esterase N in neutrophils?

<p>To break down bacterial components, released by activated neutrophils after recruitment to sites of infection.</p> Signup and view all the answers

What is the composition of the neutrophil molecule integrin?

<p>a subunit (CD11a, CD11b, CD11c) noncovalently linked to a b subunit (CD18)</p> Signup and view all the answers

What is the outcome of the activation of neutrophils in Stage 3 of the neutrophil migration process?

<p>Firm adherence to ICAMs expressed by activated VECs near the site of infection or inflammation</p> Signup and view all the answers

What is the process by which neutrophils move through the vessel wall at the borders of VECs?

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

What enzymes are secreted by neutrophils to erode the subendothelial basement membranes during transendothelial migration?

<p>Gelatinase B and elastase</p> Signup and view all the answers

What is the result of the assembly and activation of leukocyte NADPH oxidase membrane complexes in Stage 3?

<p>Bacterial killing and/or digestion</p> Signup and view all the answers

What cytokines enhance the migration of neutrophils during transendothelial migration?

<p>IL-1 and/or TNF</p> Signup and view all the answers

What is the purpose of neutrophil enzymes gelatinase B and elastase in the migration process?

<p>To erode subendothelial basement membranes.</p> Signup and view all the answers

What are the inflammatory cytokines that activate VECs?

<p>IL-1 and/or TNF</p> Signup and view all the answers

What is the role of E- and P-selectin molecules on the VEC surface?

<p>They interact with their ligands on the neutrophil to facilitate rolling.</p> Signup and view all the answers

What is the function of L-selectin ligands on the surface of activated VECs?

<p>They interact with L-selectin on the neutrophil to facilitate rolling.</p> Signup and view all the answers

What is the purpose of chemoattractants in the migration process?

<p>They cause directional migration of cells along a concentration gradient.</p> Signup and view all the answers

What is the result of chemoattractants binding to the endothelial cell surface?

<p>Activation of neutrophil integrins.</p> Signup and view all the answers

What is the role of b2 integrin molecules in the migration process?

<p>They facilitate the adhesion of neutrophils to the endothelial surface.</p> Signup and view all the answers

What are the three types of b2 integrins found on leukocyte plasma membranes?

<p>CD11a/CD18 (LFA-1), CD11b/CD18 (Mac-1), and CD11c/CD18.</p> Signup and view all the answers

Study Notes

Neutrophil Granules

  • There are three main types of neutrophil granules: primary (azurophilic) granules, secondary (specific) granules, and tertiary (gelatinase) granules.
  • Primary granules are found in young cells, surrounded by a phospholipid membrane, and contain:
    • Peroxidase (myeloperoxidase) for generating toxic bacteria-killing substances
    • Antimicrobial compounds
    • Cationic proteins and defensins that disrupt microbial cell membrane integrity
    • Cathepsin G for breaking down bacterial proteins
    • Lysozyme for breaking down bacterial cell walls
    • Bacterial Permeability Increasing Protein (BPI) with bactericidal and lipopolysaccharide-neutralizing activities
    • Esterase N, an enzyme released by activated neutrophils after recruitment to sites of infection
  • Secondary granules are found in more mature cells and contain:
    • Specific antimicrobial compounds

Neutrophil Development and Recruitment

  • Granulopoiesis is the process of neutrophil development, characterized by the sequential formation of neutrophil granules
  • The stages of granulopoiesis are:
    • Myeloblast (first cell of committed granulopoiesis)
    • Promyelocyte (azurophilic granules synthesized)
    • Myelocyte (specific granules synthesized)
    • Metamyelocyte (gelatinase granules synthesized)
    • Band cell
    • Mature neutrophil
  • Neutrophils egress from the bone marrow into circulation, where they spend 4-5 days before being destroyed during defensive action or senescence

Leukocyte Extravasation

  • Leukocyte extravasation occurs in four stages:
    • Stage 1: Activation of endothelial cells (EC) and neutrophils by chemoattractants, leading to loose attachment and rolling of neutrophils on EC
    • Stage 2: Activation of neutrophils by chemoattractants, leading to expression of b2 integrins and firmer attachment to EC
    • Stage 3: Firm attachment of neutrophils to EC, leading to cytoskeletal and morphologic change, and halting of rolling
    • Stage 4: Migration of neutrophils through the endothelium and basement membrane (diapedesis), and movement towards the site of inflammation (chemotaxis)

Adhesion Molecules and Chemokines

  • Adhesion molecules involved in leukocyte extravasation include:
    • E- and P-selectin on EC, interacting with L-selectin on neutrophils
    • b2 integrins on neutrophils, interacting with ICAMs on EC
  • Chemokines involved in leukocyte extravasation include:
    • C5a (complement activation peptide)
    • Bacterial products
    • Lipid mediators (e.g., platelet-activating factor [PAF])
    • Chemokines (e.g., IL-1 and TNF)

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Neutrophil Granules PDF

Description

Learn about the different types of granules found in neutrophils, including primary and secondary granules, and their contents.

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