38 Questions
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?
CD15, CD16, and CD11b/CD18
What is the sequence of neutrophil granule formation during granulopoiesis?
Azurophilic or primary granules, specific or secondary granules, and then gelatinase or tertiary granules
What is the final stage of neutrophil maturation?
Formation of secretory vesicles (SVs)
In which type of leukemia does DNA polymerase stain positive?
Erythroid leukemia (M6)
What is the function of neutrophils in hypoxic conditions?
Obtain energy by glycolysis, utilizing glycogen
What is the average time spent by neutrophils in tissues before they are destroyed during defensive action or as a result of senescence?
4-5 days
What triggers the expression of adhesion molecules on endothelial cells and neutrophils?
Exposure to chemoattractants
What is the purpose of the b2 integrins expressed on neutrophils in Stage 2 of leukocyte extravasation?
To attach to ICAMs on endothelial cells
What is the result of the attachment of b2 integrins to ICAMs in Stage 3 of leukocyte extravasation?
A firmer attachment and halting of rolling, leading to cellular migration
What is the direction of movement of neutrophils during chemotaxis?
Towards the chemoattractants
What structures do neutrophils use to squeeze through endothelial cells during diapedesis?
Pseudopods
What are the mediators that activate endothelial cells and neutrophils, leading to leukocyte extravasation?
Chemoattractants, including C5a, bacterial products, lipid mediators, and chemokines
What is the process by which neutrophils move through the endothelium and basement membrane to the area of inflammation?
Diapedesis
What are the two types of granules found in neutrophils, and in which stages of cell maturity are they typically found?
Primary (azurophilic) granules in young cells, and secondary (specific) granules in more mature cells.
What is the function of myeloperoxidase in neutrophils?
To generate toxic bacteria-killing substances, specifically hypochlorous acid.
What is the role of elastase in neutrophils?
To break down elastin, a protein found in connective tissues, aiding in tissue penetration and facilitating the immune response.
What is the function of cationic proteins and defensins in primary granules?
To disrupt microbial cell membrane integrity, contributing to the elimination of pathogens.
What are the multiple functions of cathepsin G?
To clear pathogens, regulate inflammation, modify chemokines and cytokines, control blood pressure, and induce thrombogenesis.
What is the function of lysozyme in neutrophils?
To break down bacterial cell walls.
What are the functions of Bacterial Permeability Increasing Protein (BPI)?
Bactericidal and lipopolysaccharide-neutralizing activities, and promotion of complement activation on bacterial surfaces.
What is the function of esterase N in neutrophils?
To break down bacterial components, released by activated neutrophils after recruitment to sites of infection.
What is the composition of the neutrophil molecule integrin?
a subunit (CD11a, CD11b, CD11c) noncovalently linked to a b subunit (CD18)
What is the outcome of the activation of neutrophils in Stage 3 of the neutrophil migration process?
Firm adherence to ICAMs expressed by activated VECs near the site of infection or inflammation
What is the process by which neutrophils move through the vessel wall at the borders of VECs?
Diapedesis
What enzymes are secreted by neutrophils to erode the subendothelial basement membranes during transendothelial migration?
Gelatinase B and elastase
What is the result of the assembly and activation of leukocyte NADPH oxidase membrane complexes in Stage 3?
Bacterial killing and/or digestion
What cytokines enhance the migration of neutrophils during transendothelial migration?
IL-1 and/or TNF
What is the purpose of neutrophil enzymes gelatinase B and elastase in the migration process?
To erode subendothelial basement membranes.
What are the inflammatory cytokines that activate VECs?
IL-1 and/or TNF
What is the role of E- and P-selectin molecules on the VEC surface?
They interact with their ligands on the neutrophil to facilitate rolling.
What is the function of L-selectin ligands on the surface of activated VECs?
They interact with L-selectin on the neutrophil to facilitate rolling.
What is the purpose of chemoattractants in the migration process?
They cause directional migration of cells along a concentration gradient.
What is the result of chemoattractants binding to the endothelial cell surface?
Activation of neutrophil integrins.
What is the role of b2 integrin molecules in the migration process?
They facilitate the adhesion of neutrophils to the endothelial surface.
What are the three types of b2 integrins found on leukocyte plasma membranes?
CD11a/CD18 (LFA-1), CD11b/CD18 (Mac-1), and CD11c/CD18.
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)
Learn about the different types of granules found in neutrophils, including primary and secondary granules, and their contents.
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